Question to ask is why leave?
There is no real talent in that weight class (as witnessed by Franklins domination, and subsequent ownage at Silva's hands) so he could be there awhile.
He goes down....he gets Matt Hughes, who I think would have a better chance then Rich did, but after watchin Matt take some pop's to the chop's by BJ Penn (and laugh them off, which he wont do against Silva) I have no confidence in Matt's standup. Matt would ground this fight from 00:02 of the first round until the end of the 5th.
If he goes up he gets Chuck Liddell. A signicantly tougher matchup for him, due to Chuck's impressive standup and even more impressive takedown defense's.
Silva's two losses in Pride were both by submission, so would think he would go up before going down to a weight class with BJ Penn, St.Pierre and the likes.