New blood in men's tennis?

Eventually, the Big Three of Federer, Nadal, and Djokovic will reach the point where they can't realistically win any more Grand Slam tournaments, and younger players will start winning more.  That time will be in the next couple of years, so the question now is:  who will be the dominant players in the post-Big Three era?

Staking an early reservation is Stefanos Tsitsipas, and he's new enough that I'm still not sure how to pronounce his last name.

Stefanos Tsitsipas comes of age at his first ATP Finals as Greek teen* defeats Dominic Thiem to cap off exciting London event

*Not sure who wrote that Daily Mail headline, but he's not a teenager, he's 21 years old. Indeed, he's still quite young.