Why does everyone assume Ennis is gone after 1 or 2 years. Most people who leave early for the NBA draft do so because they either have academic/financial problems, or are athletically superior to the competition. Ennis is very skilled, but he doesn't have, and never will have, the athleticism needed to be a lottery pick. Who is the last player you know that left early for the NBA that didn't have elite athleticism, but still was a top 15-20 pick.
Don't get me wrong, Ennis is going to be a stud in college and probably a very good pro, but that will be because he is a great game manager, team leader, and true point guard, not because he can get to the rack and finish like Dion. And from my experience these last few years, the NBA doesn't draft many 20 year old game managers with sub-par NBA athleticism. Think of Khaliff Wyatt from Temple. Dude could score against anyone, extremely smart and talented, but limited athletically. He killed everyone he went up against in college, but still couldnt get drafted. The NBA reaches based off of potential and athleticism, and that hurts Ennis' draft prospects, thus giving him a reason to stay 3-4 years at Syracuse