I really want an Azshara expansion. And no, I don't want some more "old gods are behind it all" shit. I realize that is kinda hard to do considering Azshara is working with the Old Gods, but they could easily do a good twist that would make Azshara an amazing villain.
Azshara is obviously not somebody who would take kindly to serving under someone. So what if she turned on N'zoth, and started draining his power or something? It would be something like Magtheridon (in the final raid we could even hear him N'zoth yelling and stuff). Imagine that. Azshara, betraying the ultimate betrayers. If she managed to do that, she'd look incredibly threatening. Obviously we would see Old Gods in that expansion, but instead of "well the old gods are still behind it all", we'd have a villain who managed to use take the Old God's power for herself.