Here's the thing with Peyton. He has a lot of confounding issues that may not make him such a great candidate to meet the average return to play standards of this injury. I read a retrospective cohort study last night on NFL players who had cervical disc herniation. This study had 99 players in it. Of those 99, 53 had either an anterior cervical fusion or a posterior foraminotomy to relieve the pressure on the nerve. Of those 53, 72% returned to the field to play again. This 72% that played again played on average 29 games over a 2.8 year period. Age was a negative predictor of career longetivity following surgery. What that means is that the older the player was, the less likely he would play for very long after the surgery.
With Peyton, there are some confounding variables. The anterior fusion was not his first surgery. It was at least his 3rd, and possibly his 4th surgery. He had 2-3 surgeries prior to this anterior fusion procedure. My guess is, he had posterior foraminotomies in an attempt to relieve the pressure on the nerve. There have also been reports of bone spur formation in the past, as I believe his first surgery was to remove bone spurs to open up the neuroforamen. This was in 2010. The first symptom he had was in 2006, when he may have been a victim of Gregg Williams and his bounties.
In my mind, Peyton's age, multiple surgeries, length of symptomatology, and possible co morbid neck conditions significantly decrease the probability tha the will play another 2-3 years. It will not surprise me to see Peyton struggle through one season with inconsistent arm strength and endurance problems, and ultimately retire after a season.