^^I don't think that Federer is the type of guy to retire on a high. If he wins another Slam I think his mindset will be 'I'm in good enough form to win more' rather than 'let's finish on a high'.
I think and I hope he is as you say : I don't understand and don't like the fans who ask "retiring on a high".
I like watching him play even if he doesn't win, have pleasant memories of McEnroe's and Connors's carreer ends,
and anyway getting old and declining is just a normal part of everybody's life : I think it's good to accept it
As for the OP's question, yes I've lowered my expectations about Fed since Djokovic became so great and also Nadal stayed at a very high level (and also the game becoming so physical on slow surfaces, and now we hear that the super-saturday won't be cancelled this year, which is bad news for Fed) : I used to think that Fed would still win one or two more slams, now I know it's very possible that he doesn't win one anymore.
That's why yes, contrary to what some people think on MTF, I'm very happy (as he is himself) when he wins a tournament like Rotterdam or even Stockholm
Just like McEnroe's and Connors's carreer ends.
I didn't like Sampras's carreer end because I think it didn't give a good example to common people in their life : it's very important imo that people accept getting old and declining to feel peaceful and happy (I know many people who can't accept it), and then I think it's not a right example.
Sampras made his personal choice, which I respect, he was a great player, but I hate all the comments which say that "it was the best ending ; it should be like that" : no I don't think people should think like that in their own life in general, and also I don't want Federer to retire early, even if he's number 20 in the world he will still have some good moments (I hope he stays in top-4 still for a while though)