I hope they're thinking a little bit more outside the box than just "do another province". After all it's going to be a next-gen game so the possibilities are there to be a bit more interesting than that.
Like what?
Enlighten us.
OT: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