As y'all know, I love to speculate and see nothing wrong with it, even am surprised at how some almost seem offended by speculating. That said, with Fedal we're in uncharted territory and all speculation has to be taken with a grain of salt. Historical precedents just don't seem to apply.
That said, let's look at some numbers. Roger is 36, and Rafa turns 32 the day before the French Open men's final, so will be 32 or older for every further Slam title. How many Slams have been won by 32+ year olds in the Open Era?
Only nine. Four by Ken Rosewall, three by Roger, and one by each of Andre Agassi and Andre Gimeno.
Now 2018 is a different era. Players seem to be both peaking later, and maintaining prime form later. That said, it is hard to say to what degree this is impacted by the weakness of Lost Gen. I think it is a combination: players maintaining prime form deeper into their 30s and a weaker younger generation that is exagerrating the former.
Roger has now won three Slams after age 32, two at age 35 and one at age 36. There's no reason to think that Rafa shouldn't be able to win at least one more, possibly more. But my point is, we really have to take it Slam by Slam. Look what happened to Novak; sometimes the train just comes off the rails and can't get back on (this is not to say that Novak won't recover, mind you, just that nothing is certain).
But the other thing to consider is that while Lost Gen hasn't been much of a challenge, Next Gen is looking better and better each year. Don't forget that Denis Shapovalov beat Rafa last year. Kyrgios and Zverev are both dangerous and have proven they can beat the elite. These guys, not to mention other up-and-comers like Rublev, will only get better over the next few years. One thing we can say with some degree of certainty is that Fedal will not get better. At best they can maintain their current forms for a few more years, and even then they will likely see some skill erosion, or at least more frequent injury concerns.
So while Fedal still reign supreme, the gap will continue to narrow, even if only slightly. And of course there's always the chance that Stan, Novak, and Andy come back. I mean, stranger things have happened.
All I'm willing to say is that, right now, Rafa is the favorite at the 2018 RG, and Roger - if he maintains health and form - is the favorite at Wimbledon. Beyond that, and including the USO, who knows.
:cuckoo: 
