As someone who isn't a Wake fan but has seen a fair bit of Collins and also routinely follows the NBA - I just don't see this. He's not an alien level athlete, doesn't have elite size and doesn't have a unique skillset that is extremely valuable to the NBA. In other words, his ceiling is probably somewhere around the 15th pick in the draft. 6'10" post scorers just aren't that valuable in the NBA right now (hell, even 7'0" ones aren't - look at Philly basically trying to give away Okafor and nobody wants him). Unless he grows 2-3" or suddenly shoots 40% from 3 on a huge volume of attempts while showing dynamic playmaking ability with his passing, he's just not going to be able to climb above being a mid-1st draft pick.
RJKarl earlier in the thread compared him to Marquese Chriss, but that comparison is exactly why the ceiling for someone like Collins is around #15 overall. Chriss was drafted because he's an alien level athlete who displayed a face-up game and 3 point stroke with a very raw / useless post game. He went #8 overall because that's the recipe for what NBA teams want with top 10 picks - basically the opposite kind of PF to what Collins is.
I think Collins is going to be a good pro and he's a hell of a college player, but if he gets a mid-1st guarantee ... that's basically his ceiling. Coming back to school isn't going to change the core of what he is as a player, and that just isn't valuable enough to NBA teams for him to move up draft boards too much.