Disclaimer: I do not own Fairy Tail, if I did I would make Jerza, Elfgreen, Edo NaLu and Wendy x Chelia official canon couples.
Jellal is somehow related to Makarov Dreyar.
When you think about it, it makes sense. Mashima Hiro has stated that Faust is the Edolas Counterpart to Master Makarov. Faust is Mystogan's father. So, it could be said that Jellal Fernandes could be related to Makarov. Maybe an estranged grandson or nephew?
Zeref was actually a social activist/extremist with good intentions.
If you look at Zeref's attitude during the Tenroujima Arc and during Fairy Tail Zero, he does not seem malicious or evil at all. It is showed that he warns people to stay away from him because he cannot control his "Ankhseram Black Magic." His magic sadly kills anything that touches him (or attempts to touch him) when his consciousness returns, although it didn't kill Ultear or Meredy. The theory I have is that Zeref was once a great believer in the Great World of Magic. He desperately wanted to protect humanity long enough for them to reach this "Great World of Magic," so he created Acnologica to protect humanity. When Acnologica went crazy on his dragon killing spree, Zeref created his demons from the book of Zeref to defeat him. Later, after realizing all of the harm he has done, he uses his demons from the book of Zeref to attempt a heroic suicide.
There are two more 1st (or 3rd) Generation Dragon Slayers.
For plot relevance, Acnologica can only be killed by "seven" dragons/dragon slayers. While it seemed like Laxus and Cobra are two of the most capable in the fight against the dragons (as seen in the Grand Magic Games arc) they are not "true" dragon slayers. I think Acnologica is only able to be killed by "seven true dragon slayers." Natsu, Wendy, Gajeel, Sting and Rogue's magic was taught to them by dragons to kill dragons. Laxus and Cobra's Dragon Slayer Magic was more of a way of quickly increasing their battle strength. In a far off chapter we can expect to see the seven Dragon Slayers squaring off against Acnologica. How cool would it be to have a water or ice dragon slayer joining the fight?
Laxus will surpass Makarov and duke it out with Gildarts to become Guild Master.
We haven't seen that much of a relationship between Laxus and Gildarts. We have seen a repaired relationship between Laxus and Makarov. Gildarts and Makarov have been shown to have a Mentor-Less Wise Mentor relationship (Ex. Whitebeard and Shanks). Makarov, despite Gildart's protests, Master Dreyar is adamant on having Gildarts Clive serve as the seventh master of Fairy Tail. We have also seen that Laxus Dreyar during the Battle of Fairy Tail arc really wanted to become Master. We've even seen Laxus determined to surpass Makarov ever since he was a teenager. I bet that in the near final arcs of Fairy Tail we will see Makarov once again name Gildarts seventh master, much to the Raijinshuu's ("Thunder God Tribe") chagrin. Freed will protest saying that Laxus should be Master while Evergreen and Bickslow yap on about Gildarts constantly disappearing. Makarov will then come up with an idea: Laxus and Gildarts can duke it out for the title, although Gildarts could possibly smash the Lightning Dragon Slayer yet do what he did with Natsu and name Laxus the master. It seems like Mashima is slightly foreshadowing this.
On the other hand…
What if Mashima Hiro isn't working towards Laxus being guildmaster? What if he's planning on making someone else guildmaster? What if it's Lucy? Think about it: She's arguably the most sensible and sane member they have. She also could have been left a large inheritance by her father. Which she could use to buy Heartfillia mansion back and use it as Fairy Tail's new guildhall! It'd be awesome, just imagine it. While I know a lot of people are thinking that Lucy is the weakest member of Team Natsu and while it may somewhat be true, she is skilled. She outmaneuvered Byro, curb-stomped Flare (until Obra intervened) and has the brains, kindness and leadership ability which is needed to be a guildmaster. Strength is not everything. Warrod Sequen, rank 4thamong the Ten Wizard Saints, is a part of the Four Heavenly Gods of Ishgal. Keep in mind that the Four Heavenly Gods of Ishgal are considered the four strongest mages in the country! Warrod doesn't even use any offensive magic, he has simply sustained his life by use of Green/Wood Magic for hundreds of years. Lucy, while not Four Gods of Ishgal material, is certainly a powerful Celestial Spirit Mage. This theory, is certainly a work in progress.
Zeref influenced Mavis Vermillion to found Fairy Tail in hopes of defeating himself someday.
While it has stated, as of Fairy Tail Zero, that Mavis Vermillion, Yury Dreyar, Precht Gaebolg, Warrod Sequen and Zeira(?) have founded Fairy Tail, it may be possible that Mavis had some "outside encouragement." Zeref is the most powerful, most deadly Dark Wizard in existence who has two personas: One that is evil, sadistic and vindictive and one that is calm, stoic and even kind. Zeref, foreseeing that someday his "evil" personality will emerge, presented Mavis with the idea of founding Fairy Tail in hopes of them gathering strong mages to defeat him. He may have also inspired the guild masters to create Fairy Sphere, Fairy Law and Fairy Glitter in order to defeat him.
Zeref influenced Mavis Vermillion to found Fairy Tail in hopes of defeating Acnologica.
On the other side of Theory no. 6, Zeref could have not worried about his defeat at the time. Maybe he already wrote the Book of Zeref so he could have demons to kill him. Maybe, just maybe, Zeref wanted Mavis to found Fairy Tail in hopes of them acquiring Dragon Slayers to defeat Acnologica. Another part of this theory is, Acnologica could have once been Zeref's pupil. After Zeref taught him the Black Arts and magic designed for killing dragons, Acnologica went on a dragon killing spree. Zeref, seeing how horrible his pupil had become, placed several children in the care of dragons. Knowing this would be a gamble, Zeref made sure that the children would all find Legal Guilds.
Zeref raised seven children whom he sensed had the potential to be Dragon Slayers.
Zeref, the supposed "Big Bad Evil Magician" of the series, could have actually been a father at one point. I suspect that Zeref, whom has lived for hundreds of years, had children with a woman before he acquired Ankhseram Black Magic. He witnessed the death of many people which is how he acquired his "Death" Magic, among these deaths were his wife and parents. Sensing that his time with his children would become short due to his curse, Zeref flung them into the future where the seven children were scattered and raised by the seven dragons. Igneel, Metalicana, Grandeeney, Weissologia, Skiadrum and two unnamed dragons.
Bickslow's "babies" (dolls) are the souls of his children from his previous marriage.
Tvtropes also had this theory but mine is a bit different. I think that Bickslow was once married (even happily married) to a beautiful woman after he and she eloped when they were teenagers (16 years old). They then proceeded to have babies (hehe) for five consecutive years until they were both 21. Eventually, Zeref Cultists attacked the village the family was staying in and killed Bickslow's wife. Bickslow's children were all badly injured in the fire that enveloped the village. The male widow then took his children and escaped the village. Bickslow, sensing his children were on the verge of dying, learned Seith Magic (somehow acquiring Figure eyes) and trapped the souls of his dead kids into five totem pole dolls. The order of the totem dolls in Line Formation denotes the age of the children. The one on top is the oldest and the one on the bottom is the youngest. A year later, now 22, Bickslow joins Fairy Tail. This theory would make for a sad, tragic past for our favorite possessor of human souls.
Romeo Conbolt will have his own arc.
Pre-Timeskip Romeo was adorable, Post-Timeskip Romeo was badass, now Post-POST Timeskip Romeo will have his own story arc. In spirit of Natsu's departure to train, Romeo will depart from Magnolia (sort of like how Gon departed from Whale Island) in order to become strong enough to protect his guild, much to his father's dismay. Romeo Conbolt will travel towards some sort of huge training event/mini-tournament for mages. Along the way Romeo Conbolt will make friends with maybe 2-3 people and while training with them, form strong bonds. Romeo's training will take him across Fiore, with him learning new techniques and skills previously unheard of for Fire Magic. On his way back (with his new friends) he invites them to join Fairy Tail which they gleefully accept. Returning to Magnolia stronger and more mature than ever, Romeo has one last journey to go on. The journey to help Natsu rebuild Fairy Tail.
Some choices of elements for the next Dragon Slayer will be...
Water, Ice, Sand, Earth, Wood, Crystal, Lava, Darkness (like Shadow, but purple), Dust, Smoke, Flame (manipulating hellfire; taught by Atlas Flame) and Snow.
OR the next Dragon Slayer will be an Earth Dragon Slayer, and a female to become a friend for Wendy.
We already have Dragon Slayer opposites: Natsu and Gajeel, Sting and Rogue, Laxus and Cobra, and now…Wendy and some brown-haired, green-eyed girl who can eat earth! Besides, I think that the Dragon Slayers need at least two females, Wendy needs another Dragon Slayer friend! Although, this Earth Dragon Slayer wouldn't join Fairy Tail, perhaps they'd join Lamia Scale or Mermaid Heel?
The Seven Kin of Purgatory are the Seven Sins.
Ultear is Greed: Think about it, she wants Zeref for herself (not too much of noble cause since Grimoire Heart was also Zeref too) mainly because she wants to use him to reach the "One World of Magic." Essentially, Ultear wants Zeref so she can go back in time and fix her life. That is rather greedy, she also did possess a young Jellal Fernandes and worked herself into the magic council for her own ends.
Meredy is Envy: She desperately wants Ultear's affection and love, yet feels crushed whenever she is put down by her. She also is being used by Ultear (partly), who wants the Maguilty Sense Mage to capture of at least help her capture Zeref. Ultear could have also been Envy because she was very envious about Ur's relationship with Gray and Lyon. The main reason Meredy is Envy is because she envies the way that Juvia has friends and connections with people. She is not afraid to end her own life because she doesn't have anybody to really live for (up until now) sad, right?
Kain Hikaru is Gluttony: Gluttony was hard to find in the Seven Kin except for this guy. He is pretty fat and seems to enjoy inflicting excess pain on his opponents. He is considered the most harmless of the Seven Kin, although he is perhaps their second best martial artist (after Zancrow). He isn't very smart and he gives off the appearance of an idiot—just like Gluttony from Fullmetal Alchemist. Gluttony was also considered the weak link by Ed and Al except he was arguably the most dangerous of them all.
Zancrow is Wrath: This one was easy to find. Zancrow is inherently sadistic, cruel and aggressive. He even incinerated some of Grimoire Heart's lackeys just 'cause they couldn't defeat Natsu. Also, he enjoyed torturing Natsu Dragneel during their fight and laughed while expelling and trying to kill Meredy.
Rustyrose is Lust: This one was slightly hard. Lust on one hand means a desire for sex. On the other hand lust also means a desire for power or fame or blood (bloodlust). Rustyrose has a lust for battle. He refers to Grimoire Heart as "demons," and himself as "King of the Underworld." He wants to eliminate everyone whom he considers weak.
Caprico/Zoldeo is Sloth: Zoldeo did basically sit idle for a bunch of years while Caprico(rn) did all of the Heavy Lifting. His magic, Human Subordination, allows him to summon humans to fight for him. (Celestial Human Magic)
Azuma is Pride: He only wants to fight the strongest, Erza. He thinks of Grimoire Heart as higher than all other Dark Guilds. Also, similar to Pride from FMA (or Selim Bradley), he seems to be able to "embody" trees while Pride embodies some weird dark face thing.
Flare will redeem herself by helping Fairy Tail reform (as of Chapter 427-?) and as a result will join the guild.
They've forgotten Gajeel, Jellal, Laxus and even MINERVA. Hell, if they can forgive three almost killers (Jellal, Laxus and Minerva) then they can forget Flare. She's been shown to have a sensitive side, wanting desperately to protect her home of Sun Village. I think that with a little convincing from Lucy, Master Makarov or whoever will be the master of the reborn Fairy Tail, will accept Flare as a member. Allowing Flare to finally replace Raven Tail's guild mark with the Fairy Tail emblem.
Gray actually DOES love Juvia back.
He just has a really hard time of expressing his feelings. I think that he cares about Juvia enough to save her whenever she was in danger. As of chapter 424, Juvia and Gray live together. They apparently eat, train and sleep(?) together. They also performed a Unison Raid which is said only to work between two mages with a strong bond.
There is a real lightning dragon which Laxus will have to slay.
As proof of his Dragon Slayer abilities. Some lightning dragon will appear out of the sky via magic portal (some villain will summon it) and it will threaten Magnolia and all of its citizens. Laxus, being the awesome badass that he is, will step up to the task and slay the dragon using his amazing abilities.
On the topic of God Slayer Magic…
There are no "gods," per say. Only extremely powerful wizards revered as "gods." God Slayer Magic has been shown to be taught to others (Hades to Zancrow) or be self-taught from a book (Chelia). It seems that God Slayer Magic could have been developed by Dark Mages who wanted to slay god for Zeref. Or maybe…there are gods?
Devil Slayer Magic uses the "white" or "holy" version of the elements.
It is basically the opposite of God Slayer Magic. God Slayer Magic typically uses the black or "dark" version of their element. It would only make sense that all styles of Devil Slayer Magic use a white tint for all of the styles.
Wendy Marvell and Chelia Blendy will become a couple towards the end of the manga.
They are absolutely adorable together. The two are seen playing together in Ryuzetsu Land. Wendy landed on top of Chelia suspiciously during their time together at Ryuzetsu Land. On top of that Wendy hesitates to leave Lamia Scale because she doesn't want to leave Chelia alone after Sherry Blendy (Chelia's cousin) got married. Not to mention, Chelia would be a great match for Wendy. Sky sisters, anyone?
Fairy Tail is set in the past before Rave Master.
Many people believe Fairy Tail to be set in the future of Rave Master. The un-exile of mages from Sieghart's village, the passing on of Etherion, and the dragon like races with their descendants. Although, Fairy Tail's technology is much more medieval than Rave Master (although Fairy Tail seems to be a cross between Medieval Times and the Distant Future). Zeref could be the reason why Rave Masters were even needed or the reason why Dark Bring formed, they could actually be a dark guild! Also, etherion's origin is unspecified so it could have come from the "Great World of Magic."
Mermaid Heel's Guild Master will have a large part in the story later.
That's why Hiro Mashima hasn't made her (a her, right?) have an appearance yet. He is setting her up to have a larger part in the story. In an interview Mashima said that the Guild master of Mermaid Heel may have an important part of the story. Also, Mermaid Heel is awesome! It'd be cool to see more of this guild!
Erza Knightwalker will appear in Earthland.
I know that it is considered impossible to reach Earthland since the magic in Edolas is gone. BUT, what if while summoning Acnologica or some other deadly force, Zeref (or Avatar) opens a portal to Earthland which appears in Edolas. Inadvertently, Erza Knightwalker might just happen to slip through. Not to mention out of all of the Edolas counterparts, Erza Knightwalker seemed the most interesting (in my opnion). Besides I am secretly hoping that we have Erza Knightwalker join an awesome guild like Sabertooth or Mermaid Heel or Fairy Tail, even! Bonus points if Coco, Byro, Sugarbody and Hughes get dragged along with her.
Freed likes the men.
Freed looks at 3D pictures of the Trimens from Blue Pegasus (wait for it)…naked. Yep, naked. He also seems to have a LOT of admiration for Laxus, even having a poster of the Lightning Mage in his room.
Lucy likes the ladies.
Ooh boy, we got a lot of evidence here. Let's just list all of the evidence:
Lucy looks at bikini-clad pictures of Mirajane, simply wanting to join Fairy Tail because Mira was in it.
Erza is worried about what Lucy will think of her in her seduction armor. She also crawls into Lucy's bed in Chapter 281 (Episode 165).
Levy and Lucy's friendship is bordering on romantic. Let me just quote:
"Let me see it! Please, please! Of course I'm not talking about your butt…though I really wouldn't mind…" Oh and she says "anything for my girl," when Lucy thanks her after she turns Lucy back during the body swapping episode. Oh and she quite affectionately refers to Lucy as Lu-chan (LeLu, anyone?)
Lucy and Juvia are able to perform a Unison Raid which only works if the hearts of two mages are in sync. Jellal even states that many couples have worked for years to accomplish it. Oh and they go down the Love Slide together during the 5th OVA.
Lucy with Aquarius, Gemini and Virgo. Aquarius always attacks Lucy (or wants to "punish her" *wink wink*), Virgo always wants to be punished, and Gemini turns into Lucy with a bathroom towel during the Grand Magic Games.
Lucy Heartfillia and Lucy Ashley. They look at each other's naked bodies during the Edolas arc to see if they are really the same.
Lucy peeps in on everyone during chapter 165.
Cana gropes Lucy at least twice, once in the tub, once on Tenrou Island.
Lucy and Flare's match during the GMG has Flare tying Lucy up and threatening to strip her naked. Flare also makes sure to clean every "nook and cranny" of Cana's naked body when they are both in the public bathing facility of Fairy Tail.
Well, 9 different examples. Hm, maybe NaLu isn't happening after all… (darn)
Cana likes them both.
She flirts with Eve and Hibiki and has some sort of weird drinking buddy relationship with Bacchus. Not to mention she has a crush on Macao. Also, she gropes Lucy happily, twice. She always has a Card Magic spell that summons a LOT of scantily-clad women. But this in NO way means that Cana is promiscuous. She simply is flirty.
Wendy Marvell is the little sister of Gray Fullbuster.
Thiiiiiis, is a bit of a stretch. Since Gray's entire family was supposedly killed during Deliora's attack on his village. Wendy could be the long lost sibling that was saved by Grandeeney as a baby.
Doranbolt and Nano Leaf will join Fairy Tail.
Doranbolt was revealed to have been a member of Fairy Tail all along, he just joined the council as a spy of sorts. Doranbolt (or Mest) was shown to have a close friendship (somewhat) with Wendy Marvell. Sort of a Sora and Shiro type relationship (No Game No Life is awesome). Nano Leaf was a young girl being used by the Chrono Noise Guild in order to hatch the Devil's Egg. Her magic, Egg Knock, allows her to speed up the hatching of an egg. Poor Nano even says that, "If only I could have had a different kind of Magic, maybe I could have been happy too." Well, perhaps she'll find her happiness in Fairy Tail!
E.N.D. is not Natsu himself, but a personification of Natsu's dark side.
E.N.D. is Natsu's dark side. He's everything our favorite dragon slayer could have been if he was on the dark side. Perhaps, E.N.D. will take advantage of Natsu always wanting to get stronger to protect his friends.
Natsu Dragion, Lucy Ashley, Erza Knightwalker and Gray Surge are what Team Natsu's members could have been if not for their respective pasts.
They are all what our plucky protagonists could have been if not faced with tragic pasts. Without Igneel's training or losing Igneel, Natsu Dragneel would become like the wimpy and weak Natsu Dragion. Without her father's emotional abuse Lucy Heartfillia would become the aggressive, vulgar and modest Lucy Ashley (her father wouldn't have made her so proper). Without being enslaved, Erza Scarlet wouldn't know to the full extent how precious life can be. Erza Knightwalker is Erza's aborted future, a sadistic, cruel and unfeeling future. As for Gray, without Ur's training he'd just be wearing a lot of clothes all the time. Oh and if Deliora or Ur's death never happened Gray would be a lot less reserved and stoic.
Zeira is alive and sealed somewhere deep beneath Tenrou Island.
Mavis sealed her best friend away in order to protect her life, hoping that one day Mavis can pass on Fairy Glitter to a capable mage so that they can free Zeira. Fairy Glitter, while made to vanquish the presence of any foes, it could have a secret usage: freeing Mavis' best friend. Also, Mavis Vermillion has had a tough enough past already.
Gajeel with become like Admiral Akainu (Sakazuki) from One Piece but will be brought back to his senses by Natsu.
Admiral Sakazuki is very much bordering on Lawful Good and Lawful Evil. He killed Ace, wants to put an end to all pirates (or all those who break the law) and he is ruthless, serious and stern. Sounds kinda like Gajeel when it was found out that he was a Magic Council Captain (or leader of a unit, I don't know). He didn't even seem to care that Gray was in Avatar, just wanting to arrest and defeat all of the members; regardless of previous affiliation. Gajeel could be on the path to a ruthless upholder of justice. In which case it will take Natsu and maybe even Levy to snap him back to his former self.
Shanks is alternate future Gildarts.
He's Gildarts if he was sent to the Pirate World. Or he's Edolas Gildarts.
The reason why Natsu and Gajeel couldn't get past Freed's runes is because his runes target Lost Magic as over "a thousand years old."
Dragons have been teaching humans magic since the X300's (like 30 B.C. for us) and maybe Freed's rune automatically targets those with magic whose origin exceeds 80 years.
Wendy will add Sting's magic to her arsenal, gaining a White Sky Dragon Mode.
Natsu has added Laxus' lightning. Gajeel has added Rogue's shadows. If Wendy can achieve dragon force, then she can eat Sting's holy white light.
There are seven exceeds for the seven true Dragon Slayers who were sent from Edolas to protect the Dragon Slayers, not kill them.
Queen Shagotte sent them to protect the dragon slayers, to cover up her secret love for humans, she sent 200 eggs to Earthland with the mission of "killing dragon slayers." A way of distracting all of the exceeds in Extalia.
Each time a Dragon Slayer enters Dragon Force, the closer they are to becoming like a dragon.
Sting and Rogue seem less dragon like than Cobra (whose arm is like that of a dragon's) or even Laxus (who resembles a dragon due to his scale like pattern on his body and elongated teeth). Although Sting and Rogue are the only ones who are cloaked in the aura of their own element. They also have scales that appear on their body in the form of markings. This is how Acnologica became a dragon, he used dragon force way too many times. Future Rogue could have been able to use Dragon Supremacy Magic because of this theory. Although Sting and Rogue have to be careful…they could be getting closer to becoming real dragons.
Bonus: Zeref was wrongfully accused of all crimes.
Ok, so we are being told by about EVERYONE (except Mavis and co.) that Zeref is evil. But, seriously? While, Zeref is painted out to be the most vile, despicable mage on the planet he doesn't seem threatening. He warns animals not to come near him because of his curse and even closes a dead Zancrow's eyes to give him a peaceful rest. He befriends Mavis and teachers her and her friends powerful magic. While he is the creator of the demons who formed the Tartarus Guild, he could have been the one who influenced Mavis to found Fairy Tail with the secret motive of the guild defeating him or Acnologica (depending on theory). So, what if Zeref is a Well-intentioned Extremist? (source: TvTropes) Now, let's dive right into the theory:
Zeref was a normal guy who got married, had seven kids (In order: Gajeel, Natsu, Sting, Rogue, Wendy and two others), and just so happened to witness the death of a large group of people (including his wife) while acquiring a curse. Ankhseram Black Magic, Zeref's curse, is a magic that is meant to kill any living thing that Zeref desires. However it is uncontrollable at times and it randomly kills innocent humans or animals. So Zeref, stuck with seven kids and an uncontrollable curse, makes sure to send his seven children away before something bad happened. The seven children are flung into the future (Zeref being Natsu's father would explain why he cried tears of happiness upon meeting him) and are raised by dragons, all whom know the story of Zeref. Determined to protect their children from Zeref and Acnologica, the dragons teach humans how to slay dragons; Dragon Slayer Magic. As the Fairy Tail story goes on it becomes apparent that there are seven dragon slayers (Natsu, Gajeel, Sting, Rogue, Wendy, Laxus and Cobra[?]) and that they must slay Acnologica. Natsu Dragneel is also being foreshadowed to being the one who must defeat E.N.D. and ultimately Zeref, although he has a LOT of training to do.
Well everybody, those are my theories! I hope you enjoyed them or maybe even would have agreed with a couple. Feel free to judge my theories. Oh and have a great day