I don't want to just riff off of what you said, so I'll steal your format and add my own opinions, though I think you have many valid points.
Will there be a new #1 at some point, and who will it be?
Medvedev has the points to get there. Particularly if Novak is going to focus on Majors.
@Front242's prediction will come true, I think, even if it will have taken 3 years. Meddie will be the first new #1 in 6 years, and the first non-Big 4 since, Roger first made it to #1. But he doesn't seem to have the will to stick there. Will someone else besides him or Novak reach #1 in 2022? I don't think so. But after that, I expect a trading of fortunes at the top.
Will Novak recover from the US Open and return to dominance?
I agree with your point of the yes and no. If he plays Oz, he's the man to beat. But as he focuses on Majors, and as the field below grows stronger, he will likely not be dominant next year. It bears remembering that he's done the most poorly against the youngsters of all the Big 3.
How will Rafa bounce back?
Resting his body has always served him, but time does march on. It pains me to say this, but I think he's got two years in him. If he's fit, he'll make a push for the AO, for obvious reasons. Aside from the double-career slam, it's one that has been tantalizingly close, and yet has eluded him for a second win there.
Whatever happens, he'll protect for another win at RG. If healthy, he will always be the player to beat, but there are more clay players coming up than there have been in years, and I think the field will be full of landmines. I don't expect Djokovic to be the problem, tbh.
Does Roger have one more comeback in him, or at least a farewell title or two?
I think he'll be better than his fans fear, but not as good as they (we) hope. I could see him winning Basel and
maybe Cincinnati, but not much more than that. I think it likely that this is his last year, or at least semi-full year. I could see him showing up at Basel for another couple years, sort of like Borg did at Monte-Carlo in 1982 and 83.
I kept your comment here, because I would be surprised if he keeps showing up for tournaments when he's semi-retired. I do think that this is his last year. He'll be 41 in August. Ever the optimist, if his knees are OK, I think he'll make a big push for Wimbledon. But I think his Slam winning days are behind him. Personally, I think he'll retire at Basel next year.
How high will Andy rise?
I appreciate the effort. I keep hoping that there is another big title in him. (Which you asked on another thread.) If he gets his ranking up into the 20s, then yes, I think he might win another MS1000. Particularly because the Big 3 will not be so fussed about them. Something like Cincy or Canada next summer, or one of the late autumn ones?
Who will retire?
I think Roger will. And Wawrinka. Lopez, almost surely. Verdasco. Karlovic of course. I'll hate to see Tsonga go, but he's not long for staying in. I really do hope that del Potro can make another go of it. For those who note that Tommy Robredo is still in the game, he's 39, and I don't expect him to stay in much longer.
Will there be any new Slam winners and if so, who?
I wish I had faith in Tsitsipas or Zverev, but I don't. I'd rather pick Berrettini, for being more straight-forward.
New Masters winners?
You basically picked all of the options. I'll go with Sinner.
Who do you have your eye on to make a big jump/breakthrough? | What will specific young guys do?
Again, you've mentioned all of the options. I like Brooksby, of the young US players. And I think Tiafoe and Fritz have something to say for themselves. (Not all young, but that's my take on US men's.) I watched Davidovich Fokina today, when he got beat by Brooksby. He's got a live arm. I hadn't thought much of him, but he reminds me a bit of Nalbandian.
