I could see Skyrim looking like a lot of things, there would be a fair amount of room for Bethesda to design an interesting and varied landscape that won't come off as boring and generic. While certainly, there would be a fair amount of ice and snow, that doesn't have to be all there is, however, Oblivion reduced my confidence in Bethesda's abilities to accomplish that to almost zero, and while Shivering Isles was an improvement in that area, just one expansion with two distinct sides of the map has not been enough to fully restore it, so I'm guessing we'll get something like the area around Bruma or maybe Solstheim except enlarged to cover an entire province, and while maybe that's not necessarily bad, it's hardly enough to keep an entire game from growing stale.
I have read one book in game that specifies a certain area as being a strange sort of volcanic ashland. Forget which book and which area, all I remember is that it was in Skyrim and was supposedly where the best graps (for wine) in Tamriel were grown. I'll come back with more details.
We were also promised tropical jungles in Cyrodiil based on books from earlier games, and look what came of that.