I think he is 100% correct. If he never fights again he is the greatest of all time so thats a non-issue. As far as the fight goes, He knocked Werdum down, and while bone dry dived head first into his guard to finish the fight. Stupid mistake caused by impatience. If Werdum isn't one of the best grapplers in MMA, Fedor probably gets away with it. If Fedor had been Ko'd, lost a decision or had been submitted over the course of a fight where it was obvious Fedor was not himself, then I would be in agreement that the game has passed him by. This was a loss, but it was hardly a defeat.
A win is a win, and Werdum deserved it-- He capitalized on a mistake made by a relatively mistake free fighter and made the most of it.
Of course, if Fedor loses his next fight- then it's safe to say he won't ever regain his former glory. However, unless he goes on an inept 10 fight+ KO loss losing streak like Lidell, his legacy is safe imo.