Anderson Silva is signed. They jumped the gun originally announcing it, but I believe it's official now. I could be wrong though. Nothing is official until it happens though, whether there's a contract or not, so I guess just assume it's a rumor until his name is on a UFC card.
TUF 4 guys being vets, that's only a rumor but they're filming now and according to certain websites, they claim it's going to be vets. Jorge Rivera, Tony Fryklund, Dave Menne, Patrick Cote, Mikey Burnett, Matt Serra, Chris Lytle, and Jay Hieron are rumored to be on the show.