I feel like I'm the only who prefer Atlantis: The Lost Empire than Treasure Planet.
From the narrative pov, implementing Treasure Planet is much more difficult than Atlantis because it revolves around world travelling, hence the location would be too scattered. Also I don't want to spend my time on a ship again like Never Land in KH 1 (I hate that level).
Atlantis, on the other hand, focuses only on one location which is Atlantis itself. And from narrative pov, it's much more related to KH lore since it revolves around The HEART of Atlantis. If Atlantis be featured in KH 3, this would be the first time ever we saw the world's heart instead of people's.
So yeah, I really want to see Atlantis in KH 3.