I think it’s a little too early to say. I think it’s a given that he’ll struggle, but there’s a big difference between posting a .680 OPS with so-so defense and a .550 OPS and looking overmatched in the field. If he really face plants, I could see Baltimore dropping him back down to Triple-A, but if he looks like he’s catching on rather well, they’ll keep him up and under the tutelage of the big league staff.
If I had to guess, I’m going to guess that he shows them enough to really make them think hard about keeping him up and at that point it becomes a question of cost control and competitiveness. If they think they can compete in 2013, they’ll keep him up. If injuries mount or things look grim, they’ll drop him back to Triple-A for “seasoning”, though the incentive to do that under the new CBA is much smaller than it used to be.
TL;DR: Too early to know for sure, but my money’s on him breaking camp with the O’s.