Argentine player Francisco Cerundolo believes that the era of the big three is coming to an end even if Djokovi has a few years left in him.
It's not a shocking opinion because the era of the big three is truly coming to an end. It's not even the big three anymore as it's the big two right now. Federer already retired and Nadal is one bad injury away from doing so. Djokovic is the one player that is still looking dominant but even he could be replaced by one of these youngsters. Both Alcaraz and Rune have bested him before.
As for Cerundolo, he had this to say:
"The new generation broke into the top positions of the rating. In the big tournaments a lot of finalists start appearing, occasional champions like Carlos or Daniil Medvedev. The era of Nadal, Federer and Djokovic is coming to an end, even if Djokovic still has a few years ahead."
He further explained:
"It’s a good moment for tennis, because you don’t see it as impossible. Until a few years ago you could see Nadal, Djokovic, Federer, Murray, maybe Del Potro… You could see four, five or six established players, who it was impossible to eliminate and beat in a Grand Slam or in important tournaments. Now there is a very big change in the circuit, with Alcaraz, with Tsitsipas, with Ruud… Many are my age.