As far as I'm concerned, Ada is not the villain. Derek Simmons is, and it looks like he has a clone of Ada by the name of Carla Radames which I'm assuming Chris has beef with. Also, in the new Resident Evil Damnation trailer, Ada says that she is working for the BSAA, and has been confirmed. What this means for RE6, I don't know. Ada also has an unlockable 4th campaign, so I doubt the real Ada is a villain. I'm still very hopeful for Wesker's return, so I do hope they bring him back in some way. Either that, or introduce Alex Wesker already!