Just to throw another opinion into the mix.. I think sometimes people forget how quickly giant NBA contracts can fade away. Most of the people saying he should leave now are saying he should do so for his family.. Help them get in a better place, etc, definitely shouldn't wait when you have such an easy opportunity to help them out. And I definitely agree.
But here's the thing, let's say he goes now. And let's say he's a relative bust in the NBA. This is quite possible; he goes, stinks it up in his first few years (which I think likely at his current level), maybe that gets to his head, people deem him a bust, he deems himself a bust, and things slowly fall apart. I think this is definitely a plausible scenario, if not downright likely. That means his total net earnings consist of his rookie contract, which would be generous, but not too great considering he's looking at late first round at this point.
So that's a few million dollars. Now think about it. He has a pretty big family. I'm guessing he has uncles who aren't doing so well. I'm guessing he has a grandfather who needs taking care of. Let' face it if I suddenly get millions of dollars and I have family in serious need, I'm spending that money and I am helping them out.. I'm not talking $10k... I'm talking serious help to get them out of the hole. Those few millions can disappear real fast.. REAL fast. And life expectancy is nearing 80 years.. That's an ugly 50 years with no money, no college education, no real income at all.
Other scenario, he stays for a year. Then he can re-evaluate. If his stock continues to drop or stays the same, he can stay in school for 2 more years, get a degree, and then enter the draft. I highly doubt his stock would DROP from where it is now, he will have gained a LOT of school from Matta, who is 100% interested in making him as good of a player as possible and devoting all of his time to it, instead of the NBA where it's hard to devote time to a bench player. So in the end he gets the same amount of money (but gets it later, which does suck), but at least has a degree. And personally I think he would raise his stock a bit and therefore get a decent amount more money. This means the loss is a few years of income, the gain is probably more money when he does go to the NBA, a college education, and all the perks that come from being an OSU star--endorsement money, ability to open up a bar anywhere in CBus for an easy and safe job..
He could also stay for a year and have his stock drastically improve, and then leave and this scenario has been argued by Mili... And, again, he'd get better endorsement, more college exposure and more tOSU exposure.
Anyway, I'm not saying he should definitely stay, but I do think that it is the wise decision. I think the easy quick decision is to go pro now, but I do think overall the safer choice is to go to school.. For him and his family.