More speculations:
I've always believed Bethesda has literally volumes of TeS lore, unpublished but in their vaults. I reckon the story for Skyrim was existent in at least basic form since the early 2000's, truly.
Anyway, continuing with this belief, there are a few things in Skyrim that make me think Hammerfell is next.
These things come from one quest... "In my time of need".
Don't you find it interesting that a fairly inconsequential quest, that has nothing to do directly with Skyrim, is made literally unavoidable thanks to the location of those Redguard warriors? Hmm, indeed.
And the quest, when you pursue it, reveals an amazing amount of information about the current state of Hammerfell? How there is a Redguard resistance against the Aldmeri Dominion?
Now you'd be forgiven for dismissing it as fluff back in 2011.
But let's remember... This quest is unavoidable. Bethesda wants you to do the quest.
So my prediction for TeS VI based off current information & thinking?
Setting will be Hammerfell, and the main questline will revolve around a powerful necromancer and his undead legion, the perfect weapon against the honour-bound Redguard people.
But, in addition, there will be a war quest line akin to the civil war of Skyrim, only this time it will be the Redguard Resistance vs The Aldmeri Dominion.
Thoughts?