This is how fairy tail will/should end. (in my opinion). 6/16/17- keep in mind that I've only seen up to 539 and some spoilers of 540
So the 7 slayers fight acno for like a chapter, next chapter natsu pulls through some how (without it being total BS) Natsu goes and turns into a dragon or something and fights acno on the outside. (in the spoilers I think it explained that acno's human form is in his world and his dragon form is outside) they finish it off with each of them having a huge hole in both there bodies. Acno dies. Natsu is saved from brandish and is taken far away.
Everyone thinks he's dead. next gmg fairy tail and sabertooth tie, and the tie breaker is to fight someone in a mysterious black cape with a hood who looks like a total badass.They are told that whos' ever team knocks him out first wins. They argue, mysterious guy provokes them, they are all using magic and the mysterious guy hasn't yet. They get pissed and eventually laxus or Erza or someone lifts his hood. and it's natsu, everyone is in total shock. Then he says, "come on! I'm still looking for a decent fight, anyone that thinks they can beat me is welcome!, come!!
later, after all the fighting at the gmg he explained how he was saved and how he masked his scent in order to fool the dragonslayers or something
later it ends with everyone hugging him and punching him and crap, and then in the credits Lucy, natsu co. set off to find aquarius's key.