You know, considering Disney owns all the original characters from Kingdom Hearts, I doubt the Disney content will leave any time soon.
But yeah. There are plenty of worlds that could be very interesting in Kingdom Hearts. I may not be a big fan of Disney, but even I could name a few. Princess and the Frog, The Incredibles, Atlantis: The Lost Empire, Treasure Planet, Grest Mouse Detective, DuckTales/Darkwing Duck, Phineas and Ferb, Gravity Falls, Kim Possible, Gargoyles, Marvel Comics, Star Wars, ESPN, National Geographic, The Simpson’s, Alien vs Predator, The A-Team, The X-Files, Avatar, I could go on and on.