The game isn't over yet...
I don't necessarily mean his defensive play, which I think is still fine. What I mean more are some of the chances he takes. For example, in the 2nd period against Russia, he broke up the right side, put the puck between the Russian defenders legs, walked around him and got a great scoring chance. Stuff like that will not work at the next level. That defensive player could have easily picked that puck off and turned it up ice for an odd man break the other way. NHL teams have to see that and likely won't be overly blown away by some of the things he pulls against 17 year old players.
I still think he is a great prospect and a valid top 10 pick, I just don't expect some of his bread and butter moves to translate all that well.