from sports i know (hockey), generally the next generational player is identified when they're like 12-13 years old (earlier for Gretzky). You look at the top scorers from the Brick Tournament(9-10 year old kids play in that tournament) from 10 years ago (https://www.eliteprospects.com/league/brick-invitational/201...), 3 of the top 5 scorers were drafted in the first round, and the top goalie was Team Canada's goalie at the world juniors.
edit: went back a few more years, lots of NHLers in the top 5 in scoring in the tournament, but some years are more miss than hit.
edit: went back a few more years, lots of NHLers in the top 5 in scoring in the tournament, but some years are more miss than hit.