Obviously getting something in return is always good, but IF they sign a player for the money they would have spent on Rios, then how is that not similar to a 1for1 deal? What would be the difference between (hypothetically) trading Rios for Jason Bay who is also a free agent this winter or trading Rios for nothing and getting Bay in Free agency? Really, nothing. I don't think they'll go after Bay, but insert anyone for Bay and if the value is equal or greater than Rios then it's a smart move.
I don't think we know if Rios will get better. Ya he's 28 and heading into "prime years", but we don't know. We're just basing it on the generalization that all players peak at roughly the same age.