We should be appreciative of Federer though, because we will never see anything like him again. The fact he can still compete for slams ever after the erosion of his physical skills is really a greater testament to the natural talent he has than the period of time when he was dominating the tour.
First we gotta see what happens when his voice changes.
Second, there's no big future in that kind of music, so no matter how great his voice he'd always be a niche-market success. Unless he moves in to doing other genres as well.