So I have been thinking...might be a tad dangerous I know.
One thing I found I would like to see more of in this game, is more MMO interaction in general. Not just 10 people I am an in a guild with in some dungeon. But 100 Alliance and 100 Horde fighting against the dangers that face the world. ( Zone/Instance) It seems currently the only time we get more than 25 together to fight, its Alli vs. Horde. I think the "epicness" scale of the combined Horde & Alliance vs. the "threat" would be great and would really make it awsome.
I don't mind seeing the occasional Horde and Alliance mutual joining against some some random threat, as we saw in WC3, but please keep them few and far between. Horde vs. Alliance is the very core of Warcraft. It's been there since the beginning. Orcs and Humans and the tides of darkness.