I think that if the Empire falls it won't be due to the Dominion. Sadly.... Neither to the Dunmer... Because the lizards really screwed up with my the Dunmer homeland... But I hope the Redoran will restore the country back to it's glory, and attack the lizards. ATTACK. A BLOODY ATTACK. CUT OUT THEIR SCA... Ok. Just attack them...
Anyway, back to the point... I think all of Tamriell will fall together... And the cause will probably be an attack from Akavir. I mean, Tamriel is vulnerable. Of course that it would be more awesome a Maormer invasion, but I find it hard to....
But one thing is clear to me: Tamriel shall bleed.