The entire map of Nirn is in the game,it jusn't uncessible without console commands,also the empire city is in the game.Bethesda include all the map to modders make Mods with Dlc size.
You mean the entire map of Tamerial, Tamerial in the continent, Nirn is the entire planet and we know of other Continents which are never seen. I didn't realize they generated that much of the worldmap tho, I wonder if Cyrodiil still matches up to oblivion and Marrowind to Marrowind, etc.
This said most of the cities in TES are scaled down because of hardware limitations of the games consoles, as such I don't think we will get to see an IC bigger then the one in Oblivion

. Come the next generation of consoles, the next TES game will almost certainly have larger cities since I can't see the next Playstation of X-Box shipping with anything less then 4 GB of RAM.