I desperately want Valenwood - it's an alien place, with it's walking tree-cities and ape-men, but at the same time a place that's familiar to us and filled with human-esque people.
I'm confident it's going to be Alinor though, which I'm not disappointed about. The Psijic Order would be it's Mage's Guild, and it's plot (or at least some sort of questline) would involve the Thalmor and Aldmeri Dominion. That's my theory!
We have a long wait though ... at least another four years, I'd say?
For Valenwood, if they had it set there, they'd probably have Falinesti (and any other moving trees) permanently rooted. It would probably be kind of hard to program it to move through the whole province, to make sure it always had enough space to move, to make sure the NPCs always knew where to go, to make sure it didn't crush or otherwise bug up passing NPCs or creatures it crossed over etc. Also, I only want to see Valenwood if I know they can make it really huge. I don't want to go in and see a world the size of Skyrim (game version) with trees either pretty averagely sized as opposed to gigantic or otherwise have the trees the height of a good portion of the width of the gameworld, which would just look awfully silly.