I don't remember the last three off the top of my head so I doubt they'll make it into HotS.
Mengsk, Alarak, and Duran are all on your side at some point.
Ma'lash... Maybe? There isn't a lot on him. Alarak seems like a way better choice to represent the Taalda'rim.
For other "villainous" characters we have Kerrigan, Abathur, Zagara, Tychus, and Nova (Zeratul too for that matter...). You're against them all at some point in the story just like Mengsk, Alarak, and Duran. I suppose it's a matter of degrees, but that's kind of where I was going with this.
And I think we're all leaving someone out...