I'll just say which worlds we have already seen in the series.
DO NOT WANT:
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Atlantica (For some unknown reason, there wasn't any Heartless in KH2, but there's no reason ever given. Please let this world just die.)
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Agrabah (Unless we finally get into the Palace or go to some of the places seen in the animated series. I'd love to see Genie of the Bottle in Kingdom Hearts.)
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Monstro (A Pinocchio world is something that I'd love to see, but not the fluffing whale, and it's too late to do much of anything in Pinocchio's world at this point anyways.)
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Halloween Town (Love the movie, love the world, but they destroyed its chance for coming back when they made Jack a fluffing idiot who never learns his lesson.)
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Port Royal (Never again.)
DO WANT:
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Deep Jungle (Loved the world, and they have an entire animated series to pull ideas from [though I admit that it'd be terrible if they didn't explain why Sora can suddenly talk to apes

].)
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Wonderland (There isn't much more they could pull from the film, but they could always have Disney versions of the White Knight, the Jabberwocky, the Red and White Queens, and Disney did a live action film that they could use as reference [though not make it non-cartoony like Port Royal].)
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Data Twilight Town (If they are copies of the hearts of the Twilight Towners, then they basically make a world within a world. I really did not like how we couldn't explore and see what changes were made in there. Also, it isn't like a data world hasn't been shown before: Space Paranoids. But the story or the Data Towners sounds way more depressing. It'd kind of be like Repliku all over again [with the existential crisis of the millennium].)
As far as new worlds go... I'd rather there not be another musical world, and I'd rather there not be a world that a human can't fit in (like Cars).
If Sora turns into a car. I will :|, set the controller down, and walk into the middle of Detroit and just wait to die.