I really have no idea how AJ's pro career will pan out. A lot of it will be out of his hands. He's a good, smart QB who has a knack at making good decisions, but he's also been blessed with playing with superior talent at the college level. In the pros, it's more or less equal ground, so that advantage is taken away. It all depends on where he ends up - if he lands on a team with a great OC and/or QB coach, he could be Pro Bowl material. If he lands on a garbage team that throws him to the wolves right away, and can't properly develop young QB talent, then he's toast.
If I were AJ, I'd be hoping to be drafted in the mid (or even late) first round. He's a quality QB, but too many Top Five QBs have been doomed to failure because the team that drafted them sucked so bad, and all too often there's a lot of coaching turmoil on those crappy franchises. If he's drafted by an average or even good team, and becomes a clipboard holder for a season or two to learn the system, he'll be better off for it. Having an established, experienced QB could be a blessing too. He probably won't view AJ as competition for the starting spot, at least initially. They may well have a teacher-student type of relationship and may well pay dividends.
