I listened to Cowherd this morning and I agree with him. Cowherd said that Colts must draft Luck, but if they do, they will have to do what the Packers did with their Favre & Rodgers situation, and they must choose Luck over Manning. This season, we already seen rookie QBs like Newton and Dalton doing phenomenal job with their teams, and Luck is more pro-ready than any of them. Why should he sits on the bench and learn from Manning? If Newton and Dalton can do it, so can Luck, and the Colts have enough talents for him to start winning right away. And if Luck does sit on the bench, it'll divide the fan base because if Manning struggles, half of the fans will want Luck to start and the other half want Manning to continue. It'll be just like what Green Bay went through with their QB controversy as well.
Of course, if Manning retires, this debate is moot, but I have a feeling that Manning will be back. Whether he will be 100% or not is obviously still a question mark.