I am not a fan of GSP and quite honestly I wanted him to get KO'd in all of his fights after he beat Hughes the 3rd time. That being said, I don't see how his fight with Hendricks damages his legacy (especially when considering what happened to the other fighters you listed at the ends of their careers; particularly Anderson).
Georges had noticeably declined a bit near the end (missing takedowns agaisnt Diaz, getting dropped by Condit, struggling with Shields in the standup, etc) and yet he was still able to edge out a win over a prime Hendricks.
Whether or not you thought Georges won, his performance is more impressive considering he was at the end of his career and had nothing to prove and Hendricks himself came out and shit the bed (which he has basically done ever since) when he had all the momentum in the world and really should have easily won. Now that we've really seen what Hendricks is capable of (outside of his amazing but misleading KOs over Kampmann and Fitch), I don't see how anyone can think that a prime GSP would do anything but completely embarass Hendricks in a 5 round fight. Long story short, GSP's legacy is very much intact.
Now, on topic, Aldo's win over Conor would just continue to establish his reign as the GOAT FW which he has already proven to be long ago. No one is even close in this debate (including Conor) and Aldo winning would just make him even further away from the rest. That being said, I don't think it really affects his all time P4P ranking yet as he has nearly peaked imo. He would have to go to 155 and knock off a couple of contenders to move up a spot for me because he is already like #4/#5 all time which is pretty ridiculously high as it is. It's not his fault the level of comp at FW wasn't as high but I just can't see him being higher than Fedor, Jones, and GSP. Anderson? Maybe.