Todd Howard said post Oblivion that Oblivion's art style was really inspired by LOTR. BGS really wanted to go for an authentic medieval feel with elements of high fantasy from TES.
If they wanted to go for an authentic Medieval feel, then I'd say they did a poor job on it. If they think that's an authentic Medieval feel, then I guess the designers learned Medieval history from Dungeons and Dragons.
But I think we can safely assume that not every city in Skyrim is going to look like Bruma. Even in Oblivion, for all the criticisms of looking generic directed at it, each city still used different archetecture. I somehow doubt Bethesda would suddenly make every single city look the same in the game. Though I wouldn't be surprised if we see some archetecture resembling Bruma or maybe something like the Skaal buildings in Bloodmoon, seeing as these are supposed to be representative of Nordic styles.
I do hope for some more creative archetectural designs in Skyrim than Oblivion offered, though, now, I don't expect every place to look like a Telvanni city, of course, because I really can't see Nords living in giant mushrooms, the archetecture of the game should fit with the environment and culture, but I do hope Bethesda gets a bit more creative when designing the places and styles. I don't WANT an "authentic Medieval feel with elements of high fantasy", I want fantasy. If I want an authentic Medieval setting, I'd go play an actual historical game.