It doesn't matter about which side wins. The Thalmor want a prolonged war that uses up men, resources, and time. While both sides are fighting, the Thalmor can just wait it out and eventually have an easier time winning. They kicked a lot of ass since the Empire was inept in the beginning, but when the Empire got their shit together, they started to whip Dominion ass. At this point, the people were sick of the war, and the temporary treaty was signed. Both the Empire and the Elves are trying to step into a land they don't belong in, and the Stormcloaks are sick of it. They want to be able to worship their God, and will go to war with the Thalmor after they win in the region. Even if that means they will be wiped out. If they do, it just means the Dominion fought off a smaller country of people and would still have to contend with the Empire.
It doesn't matter which side you pick if you are guessing what will happen in the future.