Silva doesn't have to relinquish his belt to go up a weight division, He's doing what BJ was trying to do (but couldn't). If silva's bored with MMA, Boxing won't hold his interest that much longer. While he may be a great mma fighter, I can't see him lasting that long in boxing, although he would probably earn quite a bit more.
I agree, the last couple of UFC's weren't that great, in fact I think I was more impressed in the sanchez guida fight night more so than the previous two events. The WEC's ok, but it just feels odd seeing the same fighters fight constantly.
Who knows, maybe the next season of TUF will be good, but I have my doubts. Heavyweights aren't exactly that amazing to watch in MMA. Boxing yes, MMA no. There are some exceptions of course like Fedor, Mirko, Andre Arlovski (when he was ACTUALLY fighting) etc... but still a lot of boring heavy weights.