I think that you will visit some towns that will be frozen. But I doubt it will last. I see it as something that will change as the story progresses. Or the ice could still be fake and that frozen town is a one time thing.
Unlike with Platinum, where the change in climate was just an aesthetic, some towns in Unova being frozen could easily be Kyurem's doing. It's not a natural occurrence, obviously. The trailer showed a building + town frozen with ice spires everywhere. I'm guessing that by the time the initial story is over and Kyurem has been defeated or captured, the ice will be gone.