Honestly, depending on any big roster moves, his numbers might not go up much next season, but we should be careful not to think he is plateauing. With Hayward coming back and the plethora of scorers on this team, the best measure of his improvements might be the eye test: watching his confidence on offense and defense, seeing how he handles the pick-and-roll, watching his confidence as he takes his man off the dribble or in the post, and generally watching his "doggedness" on the defensive end as a stopper.
I think offensive and defensive rating will show how much better the entire team got too.