Well, I'm not sure if this will get read, but what I want most:
1) NORTHREND. Seriously, I've always liked snowy areas. Northrend would be so, so awesome. Unfortunately, I think this will be saved for the third or fourth expansion. But that's a pity because I reaolly want to explore it and I don't even know if I'll still be playing by the time it's out.
Some others:
2) Hero classes (as was promised in the original WoW).
3) Siege weapons (as was also promised in the original WoW).
4) More world PvP with large objectives, like another town you can capture, for example. Tying it in with siege weapons, and making nearby battlefields with towers and graveyards you can also capture, would be even more awesome. (Possibly located in Northrend. *Hint, hint*)
5) A revised Alterac Valley that's a little more like the old version. Or perhaps a new epic battleground somewhere. Regardless, I would really like a BG that focused on the individual skirmishes and pushing the tide of battle one way or the other using a variety of tools, as opposed to simply winning and moving onto the next BG as soon as possible.