Now in next few months we will be able to have new faces in Mes Tennis as new generation is already on few players doing very good like Medvedev Zev Thiem and Tsitsipas they all capable of playing very good tennis for top 3 Federer is now going down as age factor is also going against him Nadal and Djokovic will be here for some more fun.
Those guys are really chasing the big 3 here like two years ago, yes they can win few masters tournaments, but in the grand slam, they really faltered that's why tennis is still in the hands of Djokovic, Nadal and Federer. As you can see age is not a factor for the big 3, of course they are aging, but they can play high level tennis when it matters, that is in the grand slam tournaments.
Even though Federer is 39, I still think he has a good chance of winning another grand slam. Look at Wimbledon last year, he even had 2 matchpoints against Djokovic.
He was struggling this Australian Open but was not 100% fit, especially in his match against Djokovic. The young generation is coming but I don't see anyone of these talents (such as Thiem, Medvedev, Zverev, Kyrgios) dominate ike Federer, Nadal or Djokovic have done in the past.