Young still looks like a rookie to me on defense, which he should. He's only played 38 NBA games in his life and he's 20 years old.
I was encouraged, though, that he looked like he's making progress on defense and feeling more comfortable on the offensive end, too. I expect, if he's still with the team, he'll be a viable rotation player next season and bucking for starters minutes the year after, when he'll still only be 22 years old. As long as he keeps working, there's no reason to think he won't be exactly what we thought he could be when drafted.