How I think supernatural should end in my opinion.
It should never end, but the series should end but it should have a chance for it to have a reboot.
So the final moments of the final episode of the current series should go down like this.
The brothers have settled down and married ( some how jessica came back to life and lisa remembered every thing, sam and jessica became lawyers and dean is a mechanic and live across the street from each other) and had kids, and both of them are asleep. then we see cas in heaven (they put the entrance to heaven in the playground in sam and deans neighborhood) and then we hear a woman's scream and then we see cas's face turn to pure terror because he thinks he knows who screamed. We see cas runs straight to sam's house and jog right in to the house with his angel blade out and walks up to sam's and jessica's bedroom and see the bed empty. He thinks to himself that's impossible the cars are still in the drive ways and there kid is in his bed (sam has a 4 year old and dean has a 6 month old) he then sees something red on the bed and looks up and we see's cas's eyes go wide open as he sees sam and jessica on the ceiling while bleeding in the stomach and then set on fire as soon as that happens cas runs to the kids room and wakes him up (he knows cas as uncle cas) and asks him what is going on and cas says "we need to go" and we see them run out the door before the house explodes into a ball of flames. Then we hear another woman's scream and see cas turn around and run with sam's kid and burst into dean's house and see nothing until he goes to the bedroom and sees the same thing as sam's, blood on the bed, dean and lisa on the ceiling bleeding in the stomach then got set on fire and we can clearly see this hit cas very hard and he almost screamed until dean's kid started to cry and we see cas's faces turn to complete rage then he grabs dean's kid and hold it out to sam's kids and said "take your cousin outside as fast as you can now(have not thought of a good name for the kids) go" dean's kid runs to the door as we see cas try to save dean and lisa then the scene cuts to dean's kid run outside and stop and then cas runs out grabs dean's kid and run before the house explodes into flames then we see cas holding both kids while the fire department are outside and the camera zooms in to cas's face with the face of pure rage and sadness then the scene cuts to black and the credits roll.
