Bennett's smart, and he's got talent. There's no way to say right now whether or not he'll tap into it. It could be he needs something as simple as being deactivated during a game, or having Phillips take some of his pre-season snaps to get him focussing. Maybe having the owner call him out is enough. Personally, I think if Witten were out and Bennett were actually starting and the team depending on him, we'd see his best games. He strikes me as the kind of guy who's bright and immature and has a hard time focussing in a backup role.
Either way, he's not a prototypical person, and assuming he won't have a successful pro career at this point based on available evidence is foolish.