1. He can only come back to VT if he's leaving in good standing. Based on some rumors about how he finished, seems quite possible that's not the case.
2. It's no longer free. Not much of an issue if he's making an NFL salary, but not a whole lot of motivation if that's the case either. If he doesn't have the NFL money, he could be motivated, but could he afford it?
3. All the extra academic support from the athletic department is gone if he returns.