Tough call. He won't even be in consideration to start until he gets up to speed with the playbook. EJ will definitely get a grace period so I think the earliest they will even consider giving Orton the nod is week 5, assuming the wheels come off. Then Orton needs to play like a real upgrade which is a big if. But it'd be foolish not to consider EJ's injury history.
Over: If Orton plays more than 5 games its because either EJ is hurt or an Orton led team is in playoff picture late into the season.
Under: If Orton plays less than 5 its because EJ was serviceable, Orton played poorly, or the season is lost so f@#$ it give EJ the reps.
I'm taking the Under.