Fed can say what he wants publicly but on the inside I bet he'll absolutely hate it if Nadal and/or Djokovic passes him. Don't get me wrong, it's not like he'd feel like it's the end of the world. After all, he'd still be regarded as a top 3 player of all time (with some still holding him as the GOAT), and have so much fame and money it's not even funny, along with a loving family, good health, etc etc etc. But to believe that he'll simply think "meh" if he gets passed...I'd call that being naïve.
And the same would be true if it were the other way around btw. If Nadal/Djokovic were the current record holder and someone passed them, they'll hate that too but won't say that publicly (obviously).