Well, predictions, I am going to start saying that I could not care less if he has more majors than Sampras or Federer, those debates about goats are not my thing.
Nadal just after the USO was asked about when he will consider retirement and Rafa answered "I will stop when I will lose the will to improve, to train", so basically I just want to see him enjoying his career, he knows how to win and more important how to lose.
Nadal is 24, he will probably not be able to play in some slams due to his knee problems, that's a big factor. His prime time will probably end at age 27-28.
ok, Vamos! McEnroe just after the FO was joking about "enjoying the good company while it last", Rafa had the same number of slams, "because this can change in just a month". McEnroe then predicted at least a couple more FO titles and two other major titles in other slams. I agree with McEnroe about the FO, At least 7 titles at the FO. 8 Titles will mean to break the all time record of Chris Evert.
Then at Wimby, in the next 4 years, probably 1 more or perhaps 2. And I also expected in this 4 year period at least 1 title at the AO and USO. That will make Nadal the 3rd player to win at least 2 titles in each major, Emerson and Laver.
So, at the very least, 7 FO, 3 wimby, 2 AO, 2 USO, TOTAL 14
he is in a good position to catch Sampras.
Now if you push more and try to be very optimistic, 8 FO, 4 Wimby, 3 AO, 2 USO, TOTAL 17