Sad Truth: Supernatural Has Already Spoiled The Winchesters' Grim Ending
If fans are correct in their predictions, the prequel ending is definitely going to be dark.
After returning from hiatus, The Winchesters is heating things up, apparently bringing someone very special to life and hinting that Dean is trying to change things and heal from his generational trauma through his parents' story.
While the entire storyline of The Winchesters remains a mystery (after all, anyone can be wrong about anything), many people have been led to believe that the prequel takes place in some sort of alternate universe. However, if that is the case, then Supernatural has already spoiled whatever ending The Winchesters can come up with.
In the original show's 15th season, Chuck, aka God, destroyed the multiverse, essentially eliminating all alternate universes, which would mean that the dimension in which The Winchesters take place is also doomed.
Many fans believe that no matter how the prequel story unfolds, it will end up being destroyed by Chuck, so not a single change to the canon made in The Winchesters will mean anything.
However, according to The Winchesters showrunners and Jensen Ackles himself, the prequel takes place in the main universe. If that is the case, then it is safe because it was restored by Jack when he became the new God and brought the world back to normal.
In this scenario, it's possible that the Winchesters are not just a multiversal endeavor, but rather a proper part of the Supernatural canon. However, this will still require the show to explain some of the major changes it has made to the characters' journey. One of the most painful changes for fans was how The Winchesters altered the original story of John and Mary by having John go hunting long before Mary died.
The new episode of The Winchesters will air on February 7th on The CW.