I can't really give you an answer on whats perventing the match up, perhaps Dana White is just trying to drag it out as long as he can, hes a good promoter, but I can't see it happening anytime soon, afther Georges match up with Dan Hardy, he might leave the UFC and give up his title, the reason for this is because he wants to train for the 2012 Olympic Games on Canadas whrestling team.
In this fight I can see Georges coming out on top, Silva has the best percentage of punches landed, but he's never been taken to the ground, and George has the best take downs perhaps in MMA, and he's one of the best whrestlers in the world, he only had to fight on his back once and that was against Thaigo Alves, but he showed he can work from on his back, George dominated one of the best Brizilian Jiu Jutsu fighters in the game on the ground, that as in BJ Penn, so I can see George taking Silva down and ending it with the ground and pound.
gotta love brizilian jiu jutsu!!