My speculation for a partial list of worlds that I think could be a part of the game one way or another would be (including confirmed ones):
Twilight Town (Confirmed)
Daybreak Town (pretty much confirmed)
Castle Oblivion/Land of Departure (has to be in)
Disney Castle (implied in DDD that shit would be goin' down here)
Mysterious Tower (Fantasia) (the tower part is confirmed, hopefully some more wonderful Fantasia)
Radiant Garden (it'd be weird to have a "present era" mainline KH with no Squall & the gang! So I'm saying Radiant Garden/Hollow Bastion is in!)
Traverse Town (more TWEWY, plz)
Hercules (confirmed)
The World That Never Was (preeeetty much guaranteed to be in the game)
Keyblade Graveyard (this was modeled for Back Cover so they could use it in KHIII some way)
Tangled (confirmed)
Big Hero 6 (confirmed)
Princess of Heart World #1
Princess of Heart World #2
Realm of Darkness (Aqua will have to be saved from there so I'd imagine that it's in the game in some form, maybe a short playable segment with Riku, Mickey & Aqua all fighting together to get out of there :3 )
+ 3-5 more, possibly completely new IPs not yet seen in KH (could be literally anything. Toy Story? Frozen? Zootropolis? Sword in the Stone? Lilo & Stich Earth Edition? Destino?)
Though thinking about it now, what of the Princesses of Heart worlds are even around anymore? Enchanted Dominion, Dwarf Woodlands and Castle of Dreams have all fallen to darkness, right? So there's still Wonderland, Agrabah and Beast's Castle left? So who's ready for some more Agrabah?! Or maybe we won't visit their worlds this time? Seems like if they'd be in, we are closing in on 15+ worlds in my list already and we'd have kind of a small number of new worlds, though I guess some of the ones I listed might not be fully fledged worlds but just quick pit stops, so there's still more room for lengthier completely new worlds.
Nice, see you in a year for the next screenshot.
We have Nomura's word that we'll get a lot more actual KHIII stuff from now on. The only reason we haven't seen much of Kingdom Hearts III in the last year or so is because KHBBS 0.2 has been the focus of KH hype (which is basically almost the same as them showing KHIII), so your snarky pessimism is not only ridiculously unwarranted, it just makes you seem like a butthurt, silly child.