Wait a second. I followed Carlos in his junior career, he never cramped. In fact, he has cramped in exactly one professional match and honestly explained why that happened. You claiming it's genetics and will be a long term problem is simply ridiculous. He cramped one time in his entire career and that was nerves, not "genetics."
Djoker quit many matches when young because be was exhausted and we all know he turned that around. The player who has had long-term cramping issues, including the juniors, is Rune. In fact, he's cramped on court three times this year already.
Back to OP's question - tennis will return to normal expectations after Djoker retires. 6-8 slams was a phenomenal career, Pete with 14 was considered GOAT. Alcaraz will likely end up with 8-10 majors. But its way too early to know.