I suppose I should ask, what is your definition of "not pan out"?
If you're implying he won't be an All-Star, sure, that's possible. With a player as young as Bradley it's hard to tell what will become of their career.
Bradley has all the tools to be a quality starter in the league for a long time though. Super athleticism, elite defense, hunger/drive, solid character, decent ball-handling ability and good mechanics on his jumpshot are the traits of a player who is going to last.
To be honest, I fail to see how a player with all of those traits and abilites wouldn't pan out, especially given how well he performed this year when given the chance to play significant minutes. Maybe he won't be an All-Star, but he should have a lengthy career (sans injuries) as a solid starter.