Bray is going to lose Hunter, Patterson, Rivera, and Dallas Thomas on top of playing a much more difficult schedule next year.  His maturity issues aside, people seem to forget that Bray had a great individual season.  His stats were excellent in nearly every category.  Hell, he broke Manning's single game passing yards record and threw 5 TD's in a still nearly-losing effort.  Why would he come back to a new coaching staff, tougher schedule, mostly the same players on defense, and none of his weapons on offense?
Enter the draft this year, get taken somewhere in the late second to mid third by a team that actually has some talent and can afford to coach a QB up for a year or two before giving him a shot at the helm.  That's a far better scenario than being a top 10 pick and going to a Cleveland or KC anyway.