Just over 50% of McDonald All-Americans get drafted by the NBA. That drops down into the 30% range for NBA 1st round picks. Unless your a 1st round pick you might as well come back because your not getting an NBA contract unless you make a roster, which is rare. If you leave school early as a 2nd round pick your going to end up in the D-League or in Europe, if your lucky. You look at a guy like Bobby Hansen who was drafted in the 3rd round of the NBA draft in 1983 and played 10 years. (They had 10 rounds back then) If he was coming out of college today he wouldn't of been drafted and no D-league.
Highly disagree with your level of certainty here.