I am utterly convinced that Nadal will win at least 15 French Opens. Those who don't think so haven't seen Nadal play on red clay.
Either you troll or you don't know anything about tennis (i guess you watch it since 2008 like the vast majority of the posters in this forum), the probability of such thing to happens is probably around 0,0000000001%.
It's always pointless to make such predictions, and it's basically impossible to know when we'll have a different top3 in the end of the year, so i will try de make some predictions (for the fun only) but i won't take any attention about this rule (doesn't matter if some players break the top 3)
Federer: 18 slams so 9 after 2007
Nadal: 14 slams (12)
Djokovic: 8 slams (8)
Del Potro: 3
(Too early to say for Tomic/Dimitrov/Harrison/Raonic/Goffin)