There's just something about the descriptions that make me think that it's huge. The way they describe the different environments, and all that.
I can really imagine that Skyrim will be huge! Much bigger than Oblivion. It would have to be to give the province justice. Cyrodiil would have had to, too. Vvardenfell worked well being pretty small.

I think they will be comparable in size.
I also think there will be far less places, but each place will be larger and more detailed--like Shivering Isles. This I'm getting just by looking at the screens--especially the one that shows the "explorable ruins and ancient ruins." There are only 5 cities, by the way, so I hope they are larger.

Why do you always want the next game to be bigger in size? Wasn't Cyrodiil enough? Do you know it costs money to fill that space? Or do you just want to wander aimlessly without nothing to do? Really, Cyrodiil and Vvardenfell were enough. Just get us some decent quests.