I was just thinking as the hours count down to cataclysm that this can't go on forever. How do you see the game wrapping up?
Personally I see two paths to alliance victory.
1) Varian convinces Bolvar Fordragon (the new lich king) to reassert his power over the forsaken and use his undead armies to march against the horde. With the forsaken under Fordragon's sway the horde will be caught off guard from inside and with the alliance army pounding on their gates Oggrimar will fall. With the Horde central power base destroyed, I see the remaining factions of the horde quickly capitulation (except for the trolls) and peace treaties go around, the end. Everyone's happy and healthy (except for the orcs and trolls, but nobody cares about them :-p)
2) Baine Bloodhoof is convinced to take vengence for the death of his father and duels Garrosh. Here we have an option A and B. Option A Baine wins and takes control of the horde. The tauren being naturally more peaceful than the orcs work out a peace with the alliance. Option B Garrosh wins and this mess continues indefinitely.
As for Horde victory.... Honestly I can't see any path for Garrosh to do significant harm to the Alliance without Thrall coming back and confronting him about it, in which case we have A) Garrosh backs down to his mentor or B) Garrosh gives Thrall the middle finger and a Horde civil war breaks out.
And of course there's always the Alextraza gets fed up with all this bickering and burns everyone to death so she can have some peace and quiet for once.
Of course that's just how I see it, and I know, i'm biased for the alliance but that's the tactical situations that I see. How do you see WoW ending? Horde victory? The demons come back? Kerrigan leads the zerg in an invasion of Azeroth and the Protoss purge the planet? Put it out there, I want to hear em.