Well as you know - big man training from the position your guy is in right now is detrimental to the value if you ever want to resale. Sure he will always improve your team ratings and strength but the expense per RB/ID/IS pop now is tough to calculate. He isn't far off of Division 1 standard and it might be nice to pace out his future pops so you dont suffer the wage spike from next season.
I think that there is no clear cut right or wrong decision right now. He is nicely trained and poised to become better. You need to decide how committed you are financially to him and for how long and then do whats best for your team.