I agree with the premise, that the Bills gambled and lost, but not the conclusion that the Bills can't make the playoffs next year with Losman... if the coaches are good enough, if the surrounding players are good enough, if Losman has enough natural talent, the playoffs are possible even with a rookie at QB.
As for this season and gambling, I certainly now wish that Losman had been starting as soon as he recovered from injury. Donahoe and Mularkey ended up putting a lot of money on red and it came up black when they started Drew. It's unfair, and it's hindsight, but you judge people by the bottomline.