Black Marsh is best for next TES imo.
They could base MQ around war between Argonians and Dunmer so next TES can take place on both Black Marsh and Morrowind (I know we've already seen Morrowind, but we still haven't seen Morrowind's mainland, and lot of things changed since TES III).
For TES VII, I think they could Valenwood, Elsweyr and Summerset Isle all at once (they are not that big provinces).
Still, I think that they should focus now on FO 4 & 5, and leave TES alone a bit (they should rest and meditate on what they've learned).
During that period, they should improve Skyrim with patches and DLCs until they polish it to a diamond-shine.
So their release timeline should look something like this:
TES V > FO 4 > FO 5 > TES VI > FO 6 > TES VII
You know what?
Scrap that!
Release timeline should go like this:
TES V > FO 4 >
Redguard Remake or TES Adventures II > FO V > TES VI > FO 6 > TES VII
It would be awesome if they could remake that game.
I personally haven't played it, but would really like too (heard a lot of wonderful things about it).
The problem is, it's simply too old game for my taste (it still runs in DOS).
In case a remake does not sound like a good idea, then they can make a new TES Adventures.
Plus, it would be a great chance for Bethesda to make a proper action-adventure and earn money on it, and then focus on making TES VI into a proper action RPG.
I just said they should think more out of hte box than that, not "hey guys I have a great and fully worked out idea for what the next game should be".
My point was that the first game was set over the entire continent, the second game was set over parts of two provinces with a game world the size of an actual country, then the next game was set in a much smaller but hand-crafted representation of one part of one province. It's only since then that this one game = one province mapped over about 16 square miles idea has dominated, to the extent that most people are assuming that the next game will just do that same thing yet again. All I hope is that they at least entertain the possibility of doing something as radically different to the last game as the first three did.
If you're asking me to name some specific example of what that might be then you're entirely missing my point.
Well, then the idea of TES VI being in Black Marsh with Morrowind included shouldn't be that bad actually.
Also, I wonder when will they introduce new continents to us, or anything outside boundaries of Tamriel.