Well depending on what happens in the second book (due for release on September 17) I would think that most (if not all) of the cities will be bigger. Hopefully the mountain ranges bordering Skyrim will give a good view of the rest of Tamriel. After 200 years I reckon that the Imperial city will be at least twice it's size and if you can see Morrowind, the sky would be really clean and everything looking green due to the removal of blight. Also I'd like to see Bruma from Skyrim and possibly even go there for part of a quest.
The Empire, before the death of Uriel Septim, was at one of it's highest points, if I recall, and the Imperial city was Ayleid anyway, so it was not going to get bigger. The empire has since collapsed, been reconquered and had a lot of turmoil, now a war with Skyrim rebelling. I doubt the IC will be bigger. Besides, the city in the game is merely a representation and cannot be taken as the true size so that's irrelevent. Morrowind was blown up. I doubt it will be all green and sunny. At least Vvardenfell would not have that much living on it.