According to Dana White, Georges St-Pierre will be fighting at UFC 100 this July. Unless something major happens with the Nevada State Athletic Commission's investigation of St-Pierre/Penn II (fight ruled a "No Contest"), he'll defend the Welterweight Title against Thiago Alves. I'd be shocked if this is the main event. If Rampage beats Jardine, his title shot becomes the obvious choice. There is also the possibilty of Couture/Nogueira.
You can pretty much forget the "all five titles on the line" nonsense. Brock Lesnar and Frank Mir are fighting at UFC 98 on May 23. No shot they make a 6-7 week turnaround for UFC 100.