My top 5 would go:-
I'd like to see Bisping Vs Belfort for the next #1 contender spot after Sonnen Vs Silva. It would be a great fight that we can only suspect would end in a KO. Bisping did great against Sonnen and showed brilliant defences to the wrestling. He was a little cardio sapped, which isn't really a regular occurence for him, but that is a big part of Sonnen's grinding style. Belfort Vs Bisping wouldn't go like that, so we'd see the best conditioning of Bisping throughout the entire fight.
Another controversial name I'm going to throw out there is Wanderlei Silva. After what happened with Cung Le, I see him being able to throw a spanner in the works for any title contender and should be avoided by everyone hoping for a shot soon. He got the W over Bisping two years ago and would definently have the chance to ruin his plans once again.