Silva's been exposed. It's plausible that any of the top LH's would beat him at this point (Rua, Machida, Rampage, Rashad, Jones) due to their bigger size and/or wrestling backgrounds that Silva obviously struggles with. Basically bigger Sonnens with more power and better stand up.
I doubt Sonnen would be able to do what he did again if Silva is healthy and I don't think Vitor will beat him either. The only guys that would fight him at 185 that I could see him losing to within the next 2 years would be GSP or Jake Shields. Shields has good take downs with top notch submission defense and lays and prays every bit as good as Fitch. It would be boring, but he could win a decision.