Personally, I'd like to write off Tsitsipas and Zverev, because they have become so unlikeable, though I agree that each still has a decent chance of winning a Slam. I still see Medvedev winning say, 3?
What of Thiem? Is he done? I hope not.
You've mentioned Milos Raonic a couple of times lately. He seems even more random to me that Dimitrov or Nishikori, of the Lost Gen. I don't see any of those guys winning a Major.
But, yes, the Masters are up for grabs more in part because Rafa and Novak, (and when he was playing, Roger,) started to prioritize them less. But that's not going to change. Before we see a lot of different winners at Majors, we're going to see a lot of different winners at the Masters. Pablo Carreño Busta was one of my recent favorite new winners.
Yeah, those two guys are unlikeable. But it is also hard to ignore what they've accomplished so far -- especially Zverev -- at a pretty young age. Despite their inability to win Slams thus far, they're still two of the top four Next Genners (after only Medvedev and Thiem). And both are young enough (24 and 25) that they'll get their opportunities.
As for Thiem, I personally would be worried. He hasn't won a title in two years and his "comeback" this year was rather lackluster. Still, you never know - I'd like to see him surge, and while he just turned 29 and so isn't a pup anymore, he isn't ancient. Who knows, maybe he can channel some Stanimal...but I'd bet against it.
I've mentioned Raonic because he's all but forgotten, and for awhile was one of the top Lost Genners (a dubious honor). But yeah, I don't think any of them will win a major - but I was just saying that I'd love to see one of them do a Goran. And of course Goran isn't the only player to win their first Slam or big title later in their career. Petr Korda also comes to mind; he was just a couple months younger than Boris Becker, but won his lone Slam in 1998, two years after Becker's last. And with Masters being a more open field, we might see more straggles winning at least a Masters, as we've seen with Isner, Fognini, and Carreno Busta.
Anyhow, here's the number of big titles won by the Big Four (we're including Andy), from 2002 through 2022, with bold being when they won every one for the year:
1, 2, 7, 11, 11, 12, 13, 11, 11, 11,
14, 14,
14, 10, 13, 13, 9, 9, 9, 4
(8*), 5, 4
As you can see, they won at least half of all big titles from 2004 to 2020 (with 4 of 7 in 2020 - prorated to 8), and peaked in 2011-16, then dropped a step in 2017, and another in 2021. Only 5 of 14 last year, and 4 of 11 this year, with 2 remaining. Of course most of that loss of dominance has come at non-Slam big titles, but it is still striking compared to the heart of their collective dominance, 2005-16.
So the era is clearing coming to an end - and of course Roger retiring symbolizes that, even though he hasn't won a big title since 2019. Novak and Rafa only won a single Masters each last year, and Novak just one this year. Andy's 2016 was the last tour finals won by any of them.
I was looking at their collective record yesterday and what struck me is that in some ways, 2017-22 seems like an "alternate timeline." By the end of 2016, it looked like Roger and Rafa were both done, and Novak on the downswing. If Roger and Rafa had never won another, and Novak maybe just a handful more Masters and a Slam or two after, it would have looked more historically normal. But then we had 2017-22, which totally blew all historical precedents out of the water. But the party can only go on so long, and the last half decade is sort of like the Big Three's "after party."
I think we're going to look back at 2022 as being marked by two events: The rise of Alcaraz and the retirement of Federer. So if 2017-21 was the lead-up to the changing of the era, 2022 marks the true turning point, and 2023 is the New Age...
Even though reality doesn't usually neatly fit into such narratives, my guess is that 2022 is the last year they win a majority of Slams - that at most, Rafa and Novak will win two between them in 2023, and maybe 3-4 overall together. But I've been way off about such predictions before.
Sorry but Nadal having multiple decimas 14 FO, 12 Barcelona, 11 Monte Carlo and 10 Rome is the ultimate achievement and the one record that will never be broken... True excellence, a GOD MODE level that Pushovic can only dream of. 
