The Colts have been in a gradual decline for the last few years. Peyton was what kept it going. In fact, I don't think they would have made the playoffs even with Peyton. They would have been better, for sure, but the Colts' window had pretty much closed. I hope Peyton gets to a contender.
I think they would have made the playoffs for sure. They played with some fire the first 4-5 games of the season even without Peyton and had a lot of close losses. With him, they would have kept playing and won a bunch of games.
Just MO....there really is no way to know.