He definitely has a chance to make the team, and it's a lot more than 5%. He has already made an impression in international play, and if he is close to the league lead in the Q in scoring, then he will be all but guaranteed an invite to the evaluation camp. Especially given the pressure Hockey Canada will feel from the public (at least for the invite).
And if he's invited to the camp, then he obviously has the opportunity to make the team.
Keep in mind that while they do like older players on the WJC, they often like to have at least one young player on the team who might play at the WJC for a couple of years. Getting Crosby some expose at the WJC this year - even as the 13th forward - will be valuable for him in future WJC as he takes on more of leadership role. Of course, if he continues to progress, his draft year will probably be his last in WJC play.