Save one: you have to think that if anyone's days are numbered, it's Sylvanas'. We already know she's got a bone to pick with Arthas, and if anyone isn't coming back from Northrend ali-- err... undead, it's probably her. Who would take over Undercity then-- Varimathas? If something did happen to Sylvanas in Northrend, the whole Horde might be upset, and considering Jaina may end up in on the action as well, no one's probably safe.
Still, even if our leaders get toppled anytime soon, I doubt elections are just around the corner. I don't think we really live in a democracy here-- more like a military dictatorship.