I feel it's more a case of old one giving up. Other than Alcaraz (and potentially Sinner/Aliassime), I don't see any incredible talented youngsters emerging.
In the top 20, we have a lot of decent players that will drop in and out of the top 10 (Tsitsipas, Ruud, Norrie, Zverev, Rublev..), but that is their ceiling. Medvedev is great but he's already 26 years old and hasn't done much with his career so far to be considered a danger to the greats.
Alcaraz has an open path to some easy grand slams if he keeps his current standards.
In the final, Alcaraz played well and proved himself to be a worthy opponent for Rudd. There is no doubt that he is now number one, and I also believe that this is a more deserved position. And if this continues I think he is going to keep the tag of being number one in the world for quite some time. Medvedev is a great player but I also agree that he is not someone who can pose a great amount of threat to the other greats in the game. The future belongs to Alcaraz, at only 19 years of age, he has become the number one athlete in the world. A really good time is coming up for him in my opinion.
I think it's the otherway around, it was Ruud who become a worthy opponent on Alcaraz because the kid is one of the favorite to win the US Open and he did it in fashion at 19 years old and then clinching the number 1 spot in just short amount of time.
So now we have someone on top again, and then we have Medvedev. But it is still very open as who will become the next set of big 3 that will dominate tennis in at least a decade.