I'd rather the plot be resolved in DLC, as I don't want the next Elder Scrolls game to be about that, but it's just too big. I don't even think a full-sized expansion pack would be big enough to topple an empire.
Well, they would neccesarily Topple the Thalmor, just get them out of Skyrim, and make them not want to come back I assume, or maybe the Thalmor will topple Skyrim and take it over? (And maybe as a High Elf you could side with the Thalmor,) Because, if the Stormcloaks leave Skyrim to go after the Thalmor directly, wont the Empire just come back to Skyrim and take it over while the stormcloaks are off at war?