So, I zoomed-ified on that screen that shows a new area of Traverse Town, the one that everyone is speculating leads to different worlds.
The sign on the furthest building definitely says Colosseum, but I don't think it's a portal to Olympus Coliseum. For one thing, this new Colosseum is spelt correctly. Also, over the entrance you can see two crossed battle axes and some sort of crest: the two statues on either side of Olympus Coliseum hold swords and shields. Axes, to me, represent something more medieval than ancient Greek. I think this Colosseum is something new, maybe something similar to the Mirage Arena in BBS or just the new tournament place in DDD.
As for the building on the left, I have no idea. It certainly looks Christmas-y as many have pointed out before, but not Hallowe'en Town!Christmas Town Christmas-y. ...If that makes any sense. Are there any other Christmas-themed Disney movies? For the life of me, I can't think of any that would be in KH... Could just be another random building in Traverse Town. Traverse Town likes random buildings.
Also, the Dream Eater just chillin' in mid-air. Is that Sora's Wonder Meow just currently pink or just another Dream Eater cat thing? You can't see any emblem on its stomach or floating above it like Sora's bud, so I can't tell if it's a nightmare-eating Dream Eater or a dream-eating Dream Eater. I'd say it's a good one, but why is it just...there? If you come across a random 'good' Dream Eater, can you befriend it instantly and swap it into your party?