Not to hijack here, but someone explain to me why Tilmon would sign.
There is no chance whatsoever that Illinois would not take him in the spring. Barring something that would prevent him from playing college basketball anywhere (eligibility, career-ending injury, etc) he has a spot at Illinois in hand under any conceivable or inconceivable set of circumstances. We aren't going to fill up on scholarships and there's no chance he's not the best player we can get.
But if he signs, he's locked in, and cannot entertain other offers without obtaining Illinois' permission, most importantly in the not-whatsoever-unlikely scenario that John Groce, the coach with whom he has a close relationship and wants to play for, is fired. The Tilmons aren't stupid. They know Groce is on the hot seat and they know that if he is fired Illinois will ABSOLUTELY make some attempt to play hardball with that LOI.
So what does he gain by signing? Absolutely nothing, is my read on it. I have never understood why elite prospects sign in the fall. They give the schools leverage they wouldn't otherwise have for no reason.