1) Lyoto Machida - I rate Machida highly, but Mauricio 'Shogun' Rua is a beast at 205lbs, and I do not see Machida scraping past him again. I see Shogun winning the rematch and taking the 205lb belt.
2) Brock Lesnar - I don't see Brock losing to Mir again, or Carwin; but, I do see Velasquez and Dos Santos as serious threats to his crown. Velasquez has the wrestling to defend the takedown, and could then smash Brock on the feet. Fights against Cain and JDS would be very entertaining!
3) Georges St-Pierre - GSP's not losing that title anytime soon, but if it does happen, I see Paul Daley taking it. GSP has been beaten on the feet before, by Matt Serra, and if Semtex can defend GSP's takedowns, then he has a serious chance of knocking St-Pierre out. He has tremendous Muay Thai, and is one of the most impressive technical strikers in the UFC. I still don't see GSP getting beat for a while though.
4) Anderson Silva - I see Silva getting past Maia fairly comfortably, but when Chael Sonnen gets a go at Silva we could really see him tested for the first time. Sonnen's not going to have the arrogance of Henderson and try and stand with Silva, he's going to be looking to take him down time and time again, and he's got good enough wrestling to do it. If Sonnen has a good night against Silva, he could very well win the fight. He would have to be wary of the submission, and Silva standing at the start of every round too though.
5. BJ Penn - I've not really been a BJ Penn fan until fairly recently, and I honestly do not see him losing the 155lb belt. He's getting better, his conditioning is getting better and he just looks a level above everyone at LW. Florian, Gomi and possibly Sotiropoulos could challenge him, but I don't see any of them beating BJ Penn. Almost time to move upto 170 permanently I tihnk BJ.