I don't think losing to Rashad would hurt his legacy or jumping up to 205 and losing to Jones would hurt his legacy. And if loses a decision to Michael Bisping or Alan Belcher or Chris Weidman or Tim Boetsch those won't hurt his legacy much either. What would hurt his legacy if Hector Lombard comes in and just beats the ever loving crap out of him. Fedor would have been fine and GOAT had his loses just been Henderson and Werdum but the Big Foot Silva ended his mystique. He didn't lose to someone special doing something amazing he was just beaten down. If a free agent middleweight comes into the UFC and beats him that is going to hurt him.
Anderson's legacy is not above reproach, he's made things very hard for him not based on his skill as a fighter but rather his character. The temper tantrums in the Ocatgon, the politicking on who he wasn't going to fight and who he felt he should fight, and pulling out of all the fights he's done over the years. We ignore it now....but if he loses that's going to be brought.