I think Nadal is going to win 3-4 more titles at least on the French open because he made Djokovic look mediocre last year when he won and OI won't be surprised if he wins in coming years without dropping a sweat.
Djokovic has better chances of more grand slams and even could have won US open had that foolish mistake been avoided of hitting a line person on the neck. I think since there are 2 grand slams each year on the hard court - namely US open and Australian open and since Djokovic is fit, he has better chances of leveling up and even becoming the player with most grand slams in coming time.
I agree with you, I am one of the biggest Federer supported since he started playing tennis but we have to be honest with us and he is not ready to win another Grand Slam. I would love to see a new Federer victory but he is 39 years old, we have to understand that he can not be winning titles over and over again. Then next Gran Slam victories will be leading/sharing for Rafael Nadal and Novak Djokovic and who knows if some new young tennis player is there such as Daniil Medvédev (top 3 ATP rank nad 25 years old) or Dominic Thiem (top 4 ATP rank and 27 years old).