Also, I highly doubt the Empire is going to collapse, not entirely. After all, the Mede Empire is the fourth Human Empire. The Alessian, Reman and Septim Empires all rose and fell only to be replaced by a new Cyrodiilic Empire after a short while.
Why couldnt it collapse? its not like the series needs the Empire in order to continue, tbh the Dominion could end up as the conquers of most of Tamriel, if you got ride of the Thalmor and their genocidal ideas then the Dominion would honestly be no worse then the Empire, just ruled by High Elves instead of Imperials.
As I stated before look at this Empire and look at Rome, its almost happening in the exact same way, so to think the writers are not intentionally making that comparison then your not opening your eyes enough. even how Tullius talks is how Romans acted towards the end, very uncaring about others cultures and customs, his vocal tone suggests hes tired and doesnt care anymore it has an "oh this is just another job for me to do" feel to it if you listen, he said hes put down so many rebellions implying that almost no one really wants to be part of the Empire, christ even Ulfric and Tullius' officer (Rikke) has more enthusiasim in their speeches compared to him.
the signs are there, not to mention if that second great war is coming, now they have no Emperor so with the Civil War and no leader, if the Dominion end up striking within a month of the Games conclusion the Empire wont last too long, especially seeing as the Thalmor are no fools and learned from round one and always seem to have a plan and have no doubt been watching the events in Skyrim.
also some factors to consider for the next war, they are no where near as strong as they were at the start of the first war, they had more provinces to support them (what is it now, i think just High ROck, Cyrodil and part of Skyrim?), a leader, and were not dealing with a civil war, while the Thalmor were able to grow and gain the Khajiit as allies.