Like others, Novak's performance this year was a bit surprising. I didn't think he was done, but I didn't expect him to win four of the five biggest titles or reach four Slam finals again. It is truly awe-inspiring, and while some like to focus on the fact that he's vulturing titles in a field that doesn't include Fedal, peak Murray or Stanimal, to me the overwhelming feeling is awe at him doing this at age 36 (which is the same age Roger was in his last great year, in 2017).
Other impressions...obviously Sinner taking it up a notch. Also, the top of the rankings seems to have only gotten younger, with a couple 20-year olds in the top 10 and everyone else (other than Novak) age 27 or younger. Ben Shelton and Arthur Fils are the two (sort of) new names that are now relevant.
I sort of dislike the notion that if a player is unlikely to win a Slam, then it is time to "sell" on them. I get that Slams are the big kahuna, but Masters are still strongly competitive, and I like the fact that the field has opened up a bit so we have guys like Hurkacz and Rublev winning Masters (not to mention Norrie, Coric, etc).
As for 2024, it is so hard to make predictions because I could see any number of things occurring. But there are things I'm looking for, as well as varying degrees of "Slam title likelihood." Right now I see the categories as...
Slam favorites: Djokovic, Alcaraz
Slam contenders: Rafa (RG only), Medvedev, Sinner
Slam darkhorses: Rublev, Zverev, Tsitsipas, Rune, Shelton, Auger-Aliassime (I mean, maybe?), Hurkacz (Wimbledon)
As always, I'll be watching young players and seeing how they develop. For me one of the most exciting things to see is a new young guy breaking through to another level, so I'll be watching players like Sinner, Shelton, Auger-Aliassime, Fils, and even some of the guys who seemed to have stalled out a bit like Korda, Musetti, and Fokina, to see whether they can take another step forward.