Well, they did say the world would be 20% bigger than Skyrim's world.
So I don't think that excluding Aedirn and Lyria isn't that impossible. It depends on how big they make each area.
Also, it was mentioned that it takes 45 minutes to travel from the beginning to the end of the world on horseback, didn't they? I mean, if you look at the debut trailer, the horse goes pretty fast, faster than in Skyrim, that's almost for sure. On that slow horse in Skyrim it takes maybe 10 minutes to get from Whiterun to Riften? Add another 10 to get to Solitude? I'm just fetching here, I might time it myself to see how long it takes and then post it here.
What I'm getting at however, is that this world is legitimately huge, so I don't think Novigrad will be the only city and we might very well see places like Vengerberg, Vizima, etc. But maybe on a smaller scale than Novigrad, but still there.
The places I -really- hope to see are Cintra, Oxenfurt (Redania expansion maybe), Rivia, and of course all the small countryside villages. The one shown in the VGX trailer really gave me a Murky Waters vibe, which I sincerely love. I know I'm aboard of the hype train, that's for sure.
Having a large area is one thing, it's another to make detailed cities like Vizima. I think the hype for this game is getting peoples expectations way too high. I want plenty of cities and travel to Nilfgaard and Kaer Morhen too but someones gotta actually make this stuff and the people at CDPR have limits on how much they can do. That was clearly visible in TW2.