Hopefully Summerset Isle/the Aldmeri Dominion.
The plot could revolve around the second Great War with the Aldmeri Dominion fighting on two fronts against the Empire and their allies on one side and the maormer of Pyandonea, allied with the Sload of Thras, on the other.
The Thalmor, realising that they may soon fall, wish to quickly destroy the towers preventing Mundus from dissolving before they lose the war and have overstreched their military forces across Tamriel.
As a result, their control of Summerset begins to wane, and cracks begin to form at the heart of the Dominion. Three rival factions whose only commonality is their opposition to the Thalmor have grown in secret, hoping to overthrow the oppressors of their homeland.
The Beautiful (Rielle) are altmer terrorists who hope to force Summerset to be more accepting of foreigners and foreign values through bloody violence. They are opposed to a faction of isolationists who think that Summerset needs to close itself off to the rest of Tamriel rather than impose its values on other nations. The third faction is the imperialists who support the existence of the Dominion (Summerset, Valenwood and Elsweyr in union) but who oppose war with the Empire- they want peace between the Dominion (the empire of elves) and the Empire (the empire of men).
The player can join one of these factions but needs to work with all three as well as with the Psijic Order in order to overthrow the Thalmor and prevent the destruction of Tamriel, defend Summerset from the vengeful Empire and defeat the undead and serpent hordes of King Orgnum and his sload allies.
This is my controversial opinion, but for the sake of lore consistency, I would like to see the human races removed and replaced by imga, maormer and more khajiit races: it would definitely give the game a more alien, distinct and less generic feel than e.g Oblivion or Skyrim.