Kingdom Hearts 3: 10 Worlds Fans DON'T Want To See
4. The Nightmare Before Christmas
The Nightmare Before Christmas has been one of the best worlds in both Kingdom Hearts games, but there just isn't enough content from the movies to have it appear for a third time.
Kingdom Hearts is only really just starting to venture out into making substantial original story contents for its worlds, and it doesn't seem like they'd be doing it for Nightmare Before Christmas, especially when the original film is now 25 years old.
The world of Nightmare Before Christmas is one that could very easily be expanded upon, but it's more likely that the other holiday seasons would be explored in a new movie, rather than through the third Kingdom Hearts game.
Considering a world is pretty unlikely, there is one way that Jack can still appear at least. If Jack doesn't make an appearance through a Link summon of some kind like Simba is, that'd be a real missed opportunity.
Leave Nightmare Before Christmas as a classic from the other games. It's had its run.