If Jake could ever win several gold medals and win some NBA awards, the director would be considered a visionary for talking about it in the movie, of course, the director was probably not thinking about it.
In fact, Director Crowe didn't even count on Jake being able to win the marathon at these Olympics, he just knew that Jake was really talented and that they would compete at this Olympiad and perhaps several other Olympics.
So the director was thinking more about the short-term impact that Jake could have on the movie if Jake was good at the Olympics the director could use Jake as part of the movie's marketing and attract more people to watch the movie.