From a strategic point of vew, they were winning in terms of interest during Skyrim. Even when you help either side win the civil war, the Thalmor was still winning. Well that is because there was nothing about the conditions of the Aldmeri provinces at the time of TESV Skyrim. Things might change when TESVI comes out
Exactly ^^
There's been many clues that the Aldmeri Dominion is winning. They wanted and PROVOKED the Civil War to happen to weaken the Empire even more. Perhaps the next game will be in High Rock because it's the last fully controlled province of the Empire. Maybe a war may happen in High Rock too.
I wager High Rock was never truly loyal to the Empire as the other provinces in the first place considering the Breton culture... they were always looking to advance their own benefits or protect self interests. Their "loyalty" to the Empire is merely a tool or an excuse towards that goal. If the Empire is weak, they will probably pay lip services to the Empire when the Empire is getting demolished and use the excuse of "internal conflicts" as excuse when the Empire survives or get strong or whatever...
Either ways, the Aldmeri Dominion and the Empire are not on the same page. The Empire can provide a good fight but that is all they can do at the present. The winner will ultimately be the Aldmeri Dominion. Talks about Thalmor losing control of the Aldmeri Dominion is simply unknown.
That's why if the Thalmor are the villains of ES6, they should be defeated in their own territories. Valenwood and Elsweyr merged together into one game could be the ticket.
At the time of TESV Skyrim, it seems a little hard since Thalmor retained strategic initiative and was on offensive. If their control of AD was slipping, they are most likely going to put priority in stabilizing their control of AD than wasting time on the Empire and risk fighting 2 fronts: externally and internally. It is not confirmed, but if their control of AD was slipping that is more likely to happen than not.
TESV's Empire reminds me too much of the falling Roman Empire for me to think its fate will be any different.
They are never going to set an Elder Scrolls game anywhere but Tamriel, and they certainly aren't going to make ES6 a direct sequel to an earlier game. Good news, since those are both absolutely terrible ideas.
In general, most of the "ideas" I see on this site for new games are strictly of the kids-on-the-playground variety. Those that aren't ridiculous tend to be practically unfeasible (people demanding many interlocking and branching stories that progress in real time without player input... what you're asking for is that the game become vaporware).
N TO THE O
IT WOULD BE DEVISTATING FOR THE SERIES IF ITS SET ON AN ENTIRELY NEW CONTINENT
I could see them MAYBE making a dlc that allows you to travel there but not an entire game.