I doubt Rafa will be playing, let along vying for a Slam, when Federer is "walking his boys to the kindergarten" - you realize that is 4-5 years from now, when Rafa will be 32-33? Now Rafa is such a freak that anything is possible, but one thing that seems unlikely is that he is still able to play at or near his peak at such an advanced age. I mean, look at the wear and tear right now, at 28; how will things look for him at 32-33?
I still maintain that Rafa and Roger will retire within a year of each other. Roger at the end of 2016, at the age of 35, and Rafa sometime in 2017, at the age of 31. Of course that is pure conjecture. But that would mean that Rafa has only three more years, or 12 Slams, to win his 15th, 16th, 17th and then 18th. Given the improving field, and the fact that he has missed 25% of Slams over the last three years, let's say he has 8-10 more chances. Do we really expect Rafa to win a third or more of those Slams at age 29-31? I mean it is possible, but the window will narrow, both due to his aging process and the rise of younger players.
As for Federer, not much to add that hasn't already been said. I said a couple months ago that I didn't think he had that extra edge to win another big tournament, but then he went ahead and won Cincinnati. He made it to the SF or later at three of this year's four Slams and I think he'll be in the mix again next year. As some have said, if anything the open field improves his chances as it also means that Rafa and Novak are more prone to be upset earlier on.
That said, the US Open is disappointing as it is hard to imagine a clearer shot at a Slam. But that disappointment is leavened by the fact that we'll have a new Slam champ this year.
But if I had to put a percentage on whether or not Roger wins #18, I'd say something like 30%. Not enough to say "probably" but enough to say "worth hoping for."
