I doubt Caleb Hanie will enter the season as the #2 QB. I don't even think he should be on the roster. Brock Osweiler's "season" will be limited to training camp and preseason. He would get much more reps and playing time before the season if the Broncos were carrying 3 QBs. I have no idea how much Peyton Manning will play during preseason. He must finish his rehab and take care of his body, but he must also test this offense and his timing with the receivers. Anyway, once he goes to the bench, it will be a mess to split the remaining playing time among Hanie, Weber and Osweiler.
Hanie spent 4 seasons being developed by the Bears, and the result was a disastrous performance in 2011. I think the Broncos should take a good look at Weber and Osweiler during training camp and preseason, allowing them to share 2nd and 3rd team reps. Osweiler was drafted in the 2nd round, a big investment if you realize that Peyton Manning has a sense of urgency. He could have received more help from the 2012 draft. If Elway decided to sacrifice immediate impact to develop a QB of the future, then Osweiler should get plenty of reps before the regular season starts.
When you have 3 QBs behind the starter, it's hard to give a fair opportunity to all of them. Weber, as the #4 QB, threw 1 pass last preseason, in the 4th game. I would keep 3 QBs and carry Weber as the backup QB only if he can beat Osweiler, otherwise he should return to the practice squad, with Manning and Osweiler as the 2 QBs on the final roster.