Friend in a "vegetative state"?

Okay so I have a friend who was in a really bad car wreck and Im not exactly sure what part of his brain he hurt but I know it was his brain stem & something with his equilibrium. Well it's been two months since the wreck and he is still in the hospital, at first he was in a medical induced coma because of all the head trauma.. But now he is what they said almost a vegetative state because he has sleep cycles and he wakes up but he does not respond. Like if you through a ball at him, he doesn't feel it. But I very much so think he can hear us. I talk to him all the time and he moves his mouth like hes trying to talk to me or he kicks his right leg. Everytime he tries to talk he'll start to cough really really bad, so I Think that is a sign that he is trying to talk. Also the other night I sware he mouthed bye to me.. Its so sad I cant even sleep hell its 4:23 in the morning and I can't sleep because of it.. He is getting moved to a rehab place in Houston this week.. wich is about 4 hours away, but anyway (im ADD), I'm wondering when he does ( because HE WILL ) come out of this, will he be the same person as before ? Will he remember things while in this "coma"? Whats going through his head? How long should this go on for ? Also he is 18, which is in his favor. Also he curls his arms inward ... I just want as much information about this as possible..