That's a question I've been asked more times than I can remember. It usually starts with numbers: "coach, do you think one day I will deadlift 700lbs?" It invariably evolves into titles: "do you think I can break the all time record?"
The honest answer is always "I don't know".
Athletic performance is a product of too many variables we know of, plus some that we don't know of. That's why talent screening in sports that have commercial value is a sophisticated activity but it still depends on the availability of a large talent pool. Talent screeing is never about an individual, but how to sort out several individuals whose genetic, physiological, and psychological indicators are optimal to one specific sport. We still have no way of predicting how each selected athlete will perform on the long run.
Some scholars suggest that we don't have enough longitudinal studies to improve prediction. Other studies focus on one or more variables that we can measure such as muscle fiber compostion, psychological factors such as confidence, grit or anxiety. At the end of the day, it remains unpredictable.
Could anyone have predicted, fifteen years before they were considered the best of all time, what Serena Williams, Michael Jordan, Amanda Nunes, Jesse Owens, Martina Navratilova, Ed Coan or Pelé would become? No. But a couple of years into their respective careers could provide a decent guess.
I've seen "athletic wonders" that never achieved anything. They showed a lot of potential. Actually, they showed such exceptional potential that a lot of expectation was immediately was created. Maybe that was the problem: they couldn't deal with that. Or maybe they really didn't have enough of some unknown performance variables.
Some are gritty enough and progress in a fast and steady way until they stop or they slow down significantly. Not all the new tricks, methods, nutritional strategies and ergogenic fads get them into the progress rate they showed when they started.
Sports fans and spectators, as well as novice athletes, have no idea about this. They focus on the names of the stars in their sports but they ignore the many thousands of "promising talents" that never made it.
Coaches know that and they work with a large number of athletes. Some will make it, some won't. One in several million may become the next Amanda Nunes. No experienced coach counts on it.
That's why I prefer to focus on the athlete's autotelic enjoyment (enjoy the sport for the sake of it) and intrinsic motivation. It's wise to avoid motivational lies about success. If one in a million will make it, these competitive lies will hurt a million minus one.