If one is drafted and accepts a professional contract the scholarship is null and void, the admission to the school is not.
You must enroll and attend classes by first semester of your acceptance or you are considered a no show.
I am not sure how long an admission is held for future, most likely one would have to reapply again, it's not like he has attended classes and worked towards his degree, which would become a withdrawal and I do beleive their is a time frame for that possibility before one has to reapply.
Hope this helps.
Also understand the it is very difficult to start your education while playing professional ball, unless the school is on the 1/4 semester, most schools begin in august and pro ball does not end until late august or early september if the team makes playoffs.