For his player to get to 100k salary will take about 5 seasons. By that time he can easily be in D3. In every D3 around the world it is very possible to have a 100k salary player assuming you have managed your team and arena properly.
Why not trade him out now for someone with even MVP potential, or Superstar potential then? You would get an easy million profit, and still have just as good a trainee.
If he were to trade him in for a MVP or Superstar he would have a very small profit of a maximum 1 mil with most likely worse starting skils. His trainee is perfect 6'0" and great starting skills. Your not going to find something comparable if he tries to get another US trainee (To match the Merchandizing revenue he would lose by getting a foreigner).
I don't think he is going to promote to the NBBA in successive seasons, which means he is going to stop being able to afford the salary at some point.
It will take well over 6 seasons for the salary to hit a level of unreasonable. It would be much better to stop training a player by choice than be forced to by a cap when you need that player to become better still.