This post was spurred on by some discussion in another thread about Skyrim's Civil War.
I read through UESP and noted the allegiance of each country:
Hammerfell = Independent
Black Marsh = Independent
Morrowind = Independent
Skyrim = Empire or Independent
Cyrodiil = Empire
HIgh Rock = Empire
Valenwood = Aldmeri Dominion
Anequina/Pelletine (Elsweyr) = Aldmeri Dominion
Alinor (Summerset Isle) = Aldmeri Dominion
So 3-4 countries are independent. 2-3 are ruled by the Empire. 3 are ruled by the Aldmeri Dominion/Thalmor.
In VI the state of Skyrim has four separate potentials. It could be Aldmeri Dominion controlled, it could be Empire controlled, it could be Independent, or it could be split with half given to the Stormcloaks and the other half ruled by the Empire.
I highly doubt the Aldmeri Dominion will control it. I kind of get the feeling that that Skyrim will either be Independent or half-ruled in the next title.
Here I want to figure out what kind of position all the nations are in and if they can defeat the Aldmeri Dominion.
Hammerfell = Weakened by its recent war with the Dominion.
Morrowind = Weakened by losing Vvardenfell due to (super)natural events and suffering a huge loss due to the Argonian invasion.
Black Marsh = Recently gained Morrowind territory. Strong. Ruled by the Hist(?). Would probably die fighting before joining the Dominion.
Skyrim = Weak due to the dragon attack and the Civil War.
Cyrodill = Steady.
High Rock = Steady.
Valenwood = Firmly under control of Aldmeri Dominion, steady.
Anequina/Pelletine = Split by Dominion, steady. Kind of an uneasy alliance though, the Thalmor won the Khajiit over with a lie. If there's any doubt about the Thalmor or if their actions are determined false, there could be rebellion. The Thalmor just need to keep them happy so they can move troops through Khajiit territory.
Alinor = Aldmeri Dominion, capital, strong.
Potentially, the independent countries could form an alliance to fight the Aldmeri Dominion, not sure if they would fight or ignore the Empire though (maybe they will help the Empire but remain separate?) Skyrim, Morrowind, and Hammerfell could form an alliance (unlikely with Morrowind though). The Black Marsh would probably stay independent as they hate the Dunmer, unless the Hist felt that the defeat of the Aldmeri Dominion was necessary. The Argonians also supposedly hate the Khajiit so that's a reason for them to fight the Thalmor.
By itself I don't think the Empire could do much as they lost many territories and may remain with only two countries in VI. With High Rock being geographically isolated from Cyrodiil I don't see them being able to manage both nations well. I think the Empire will need help from the Independent nations in the next title or else it may be defeated if the Aldmeri Dominion makes a move.
The Aldmeri Dominion has Valenwood, Anequina/Pelletine, and Alinor, but I don't believe they have a strong hold on what was Elsweyr. If they defeat the Empire they could easily spread their influence once again through Cyrodiil. I can see the next game being about taking the fight to the Thalmor and fighting for the Independence of Valenwood, shortly after some event effects the nationality of Anequina/Pelletine. The Dominion may be driven back to Alinor and be forced to surrender if all goes well. If Black Marsh decides to help either the Empire or the Independent states then I think there is a lot better of a chance for everyone fighting the Dominion.
There is also the chance that VI takes place sometime before 4E 200 though. Maybe it could be about the uprising of the new Aldmeri Dominion?