Yes, I agree
@Federberg. I feel that Thiem is one or two years away from surpassing Rafa on clay. He'll get a bit better, and Rafa will get a bit worse and they'll meet in the middle. And of course it is a long way from now until Roland Garros 2018 and a lot can happen.
But aren't you contradicting yourself bit? I mean, yes, modern conditioning techniques and technology is seemingly extending careers, but younger, stronger, hungrier players always arise - and isn't that part of the historical perspective? In other words, I don't think it is one or the other - either they'll revert to historical norms or they'll continue to win indefinitely because of modern stuff. Maybe it is a bit of both? That is, maybe the normal aging patterns are just being extended by a few years. But as I've said before, we'll know more in a two or three more years as Roger's generation is largely retired, and those that remain are mainly journeymen outside Slam seeding.
One thing we have to also keep in mind is that the generation that should be peaking now--those players in their mid-20s, or 22ish to 27ish, born 1989 to 94 or so, are quite weak as a group. The entire cohort is in danger of being leap-frogged by Alex Zverev (born 1997) and his posse. This weakness has facilitated greater dominance on the part of the Big Five, in my opinion.
So my view is that we're BOTH seeing something unprecedented AND historical inevitables will eventually assert themselves. The Big Four might hang on and dominate for another year or two, but certainly by 2019 or 2020 Zverev etc will be taking over. In fact, I think next year we're going to see Zverev joined in the top 20 by several more young players: Khachanov, Medvedev, Tiafoe, and Rublev are all rising, with Ruud and Shapovalov not far behind. And perhaps others.
But before I go on too long, here's an interesting part: the second tier guys like Berdych, Ferrer, and Tsonga are being replaced by the best of younger generations. Already Nishikori and Raonic have established themselves as top 10 guys, Thiem among the slightly younger players, and Dimitrov is on the cusp. Zverev is also about to creep in, and possibly Goffin and/or Pouille. But as this is happening, the same old Big 4/5 stay at the top...my point being, the sea change is happening, just below the surface (elite). Eventually their hegemony will be broken...I mean it has to, right? Right?!