TW3 isn't only No man's land and Skellige + Novigrad. It will also feature some smaller, story-relevant hubs (probably Kaer Morhen, Vizima, flashback scenes,...)
The problem with seamless open worlds is imo staging, pacing and complexity. If you have a complex story to tell with a lot of choice and consequence in a kind of realistic fashion, it's better to narrow down your locations to reduce overall complexity and to enable focused level design.
That's still one of my biggest concerns with TW3, that the world is already too big and too connected...
Yeah I was thinking of big areas but if it had fit the lore map; like all -needed for story- locations was near the main regions of the game and included in one of the big maps, I don't see how it would take away from the game. Story blockades are already there and can be used more often for pacing. Simple logic suggests: If "staging, pacing and complexity" can be done in the current big areas, couple more included locations wouldn't change anything. But game which is loyal to lore map is already there and we're hypothesizing here for nothing good for it