The only fighter I can see beating Silva as of this day in age is Yushin Okami, he has all the tools and right mind set to defeat Anderson Silva.
All this talk about GSP moving up a division and fighting Silva at 185 is crazy talk as of right now, hes got to fight Diego Sanchez, John Fitch and Matt Serra before even thinking about it in my opinion.
At least 2-3 years in my opinion before he potentially goes up to 185. He walks around at 190 though I believe so it could happen sooner then I think, but that's my opinion on that.
As far as someone beating Anderson Silva within 08-09, Okami is the only one that comes to mind. I said that Okami was the one to beat Silva back when Silva beat Rich for the first time. Okami is big for 185, hes a huge dude. That and his skill set and the heart he progresses; hes a defiant candidate to beat Silva.
I'd be in favor of Okami catching Silva in a surprising submission.