For one, he is putting up these numbers, as awesome as they are, against low level competition and/or smaller players. He needs to prove himself against big 10 players.
For 2, I don't know that he was as hell bent on getting drafted last year as everyone thinks he was. I think Rosie coached him up as if he were interviewing for his first job right out of college. He stated many times that he was willing to do whatever was asked, even if it meant being the guy at the end of the bench, etc. any team that would take him...
My point is that he went at it with a business like attitude, listened to the experts and came back and has improved, especially in the areas that he was told he needed to. Don't get me wrong, had they told him he was a first rounder I think he would have left. However, they didn't, so he came back. I don't think it was that hard of a decision for him in reality.
All that being said, I think he takes the exact same approach this year. If he earns his way into the first round, he is gone. If not, I think he comes back. As someone else said, he isn't even on a draft board yet. But he does have plenty of opportunity to up his stock. I say it's 50/50, we will see. What I HOPE happens is that he is national player of the year, we win the championship and he is the number one pick. But I doubt it...