At best he is a 2nd or 3rd guy off the bench. At worst he will be out of the league in three years. What happened to all of those who were talking about him as a rookie of the year candidate?
Right now I think he's pretty good as a 4th big who can play at either big spot. I think he can develop into a quality 3rd big.
I don't agree with you about him being out of the league in 3 years. He's got too much skill to go with his size, and he's shown that he can be a solid rebounder despite having more of an outside game on offense.
Big guys who can shoot the three and aren't total stiffs in other areas of the game tend to stick around for a while.
At the very least, he's as good as Anthony Tolliver, right? That guy finds a job every year.
Regarding the ROY talk, I don't think it was crazy to think he could be a challenger, at least. The trouble for Kelly is that he's had some nagging injuries that have kept him off the floor, and he's also got significant competition for big man minutes on this team.
If he had been 100% healthy from day one and played 28+ minutes a game despite his ups and downs, I think he'd be putting up solid "counting stats" (not saying he'd be efficient or good on defense).