I am usually one to advise kids to go as soon as they are sure to be drafted, but in Fab's case, I think it would be a mistake. Although he is old for his draft class, he is still very inexperienced. He will need a lot of reps to get better. It would be very easy for him to be drafted into a bad situation where he never gets those reps and is out of the league after his first contract expires. He is one of the few cases where I think he should return even though he is a likely first rounder (although there is no way he is a Top Ten pick - anyone who drafts him knows they are picking a backup center whose only current NBA skill is blocking shots, but still knows very little about the game and is the product of a zone defense -he's probably going in the 20s).
Kris is a borderline first rounder but I think he ends up dropping to the 2nd round.
Dion has certainly played himself out of the first round and probably out of the draft entirely, unless he has a monster post season.
I think Scoop is the most intriguing prospect of all. He is having a terrific season and has shown himself to be a leader and a very heady point guard. His age works against him - he'll be 24 this summer, one of the oldest guys in the draft - but his size, experience and skills are working for him, and there is always room in the NBA for solid backup point guards. Unless he screws the pooch in a tournament game and sends SU home early, then someone is going to take him in the 2nd round, and I would not be shocked to see Scoop end up having a six or eight year NBA career.