I'm really curious about that place right under Driftveil City. I guess it could be a new City. Although doesn't it seem really close to Driftveil to be a new City? I'm think that since Drivtveil got destroyed, because of the two giant craters, I'm think it is Driftveil, a re-built Drivtveil. Since Driftveil got destroyed, everyone moved there and started rebuilding.
Also, I'm going to say that there's going to be a new City on top of the Mountain in Eastern Unova, near the Abundant Shrine. There seems to be a new structure up there.