After this growth spurt, the growth plates in the bones fuse, and there is no further increase in height. Although most boys have gotten to this point by 17, a few have not, and therefore will continue to grow even while in college. On the other hand, boys who go through puberty on the early side will have completed all of this by age 14 or 15, and then not grow any further.
Since you say your son hasn't grown in the past two years it seems more likely that he has completed his growth already, but no one can say this for sure without examining him to see if he has gone completely through puberty. If he is still is only part of the way through puberty then further growth is possible.
I recommend that you take him to see his pediatrician or an adolescent medicine or family physician (not a physician who treats only adults) with your questions. That way he can be examined, and get a more accurate assessment of his weight, height, stage of puberty, and general health.