Seeing as how the general trend of BGS is to shrink the game world as time progresses, I doubt the number of towns, or even the map size for that matter, will be overwhelming.
Oblivion was bigger than Morrowind, but it didn't feel like it. Mostly because Cyrodiil was bowl-shaped and incredibly easy to travel through. I have a good feeling that mountainous Skyrim will remedy that.
While I agree with you on Bethesda making wonderful sandbox games, correct me if I'm wrong, but according to lore, shouldn't Cyrodiil have been a dense jungle-like area?
You'll notice I never said they were very good at following lore :whistling: