Djoker owns the head to heads against both Roger and Rafa.
That is an incredible reality. He is also younger than both.
Rafa is unlikely to win another major outside of the French (where he won 11 of his 17 Majors). He may have 2 more French's left in him, but my guess is it is probably only 1. His body is just not doing him any favors. Too many years of grinding on the knees and flinging the wrist. The way Djoker played in the Aussie final, he would have beaten Rafa in straight (or maybe 4 sets) on the Clay.
Roger is unlikely to win more than 1 more period. He just does not do as well in the required seven 3 out of 5 set matches anymore. As an older guy, it is tougher to string 7 great matches together. He has more "bad" days. He has to play at his very top level to win against the top 6-8, which did not used to be the case.
Djoker will catch Rafa in total Majors. Even odds he catches Roger, if his elbow stays in good shape (as appears to be the case with the surgery early last year). With Murray retiring, the only other active players who have won a Major are Wawrinka (3), Cilic (1), and Del Potro (1).