I'm a QC (quality control) player for SC2. I've beaten an early version of the game, here are some huge spoilers, read at your own risk. Spoiler Jim Raynor and Zeratul are able to turn Kerrigan back to her human self through Xel Naga technology. Later she helps them fight the zergs. She is no longer the Zerg leader in Heart of the Swarm, it's a surprise. Spoiler Tassadar makes a return. Via Xel Naga gateway, he is reborn, only this time stronger and more powerful, sort of like Gandolf the gray turning into Gandolf the white on his return. That's it for now, if you want to know anything else, let me know there are other big twists too, but i will not reveal them.
I'm calling bunk on these, simply because if you were a QC tester, you just violated a huge NDA and are likely to be sued?
Spoiler I somehow believe this, at least the part about kerrigan, especially after seeing that one artwork pic of her having a human skin complexity, lying on the floor. If what he says is true then Starcraft 2 Storyline is going to be EPIC. I am more interested to learn more about the Xel'Naga, the hybrids, the artifacts, and all the different factions surrounding these mysteries.
that would make for epicness, hard to resist, but no matter of the spoilers, campaign is goign to be so awesome, cant wait for the cinematics