Will the Xel’Naga make a stunning return in StarCraft 2? That would be awesome, especially if they decided to destroy the races they once created, thus forcing everyone to work together.
Also, I can't help but think that we'll see some wierd human/protoss gene splicing, done in secret of course. Or maybe Raynor will get it on with a protoss chick and have a little Franklin Richards megaton baby.

Could Kerrigan launch a massive attack on the Terran like she did to the protoss in Brood Wars?
And, will Earth play any role in this one? Like, will more colonists/prisoners find their way to the Terran planet, or even better: what if Kerrigan finds a machine that can send the zerg to Earth, and you have to stop her? DUN DUN DUNNNNNNN