In general (on a competitive playoff team, with a star #2, #2 in perimeter defensive duties etc), I'd estimate around 30-33 ppg. His approach to the game would be different because of coaching, improvement in defensive schemes/defenders, improvement in offensive schemes/offensive players, landscape, and the natural evolution of the game.
If we're talking best case scenario where he gets to put up as many shots as he wants, on a lottery team, on high minutes, it'd be around 35-37 ppg. Similar to what Durant, Curry and LeBron could average if they were put in the same position.