Of course it could happen. However, teams like the Steelers have been mediocre at parts of their mini-dynasty due to horrific injury issues. Aside from Hernandez, that doesn't seem to be the case as of yet. The team just hasn't been consistent offensively or defensively at any period of this season. Another game like that, especially against a team that we should beat handily, would put us at 1-3. Historically, with Belichick and Brady at the helm, that would be a position that we have hardly EVER found ourselves in even with extremely sub-par squads. If that doesn't signal the downswing of a dynasty, then I don't know what does. Let's not forget that, in your example, we would be sub-par with Brady turning another year older and closer to 40 next year.
Sorry, but the Bills are still pretty bad. It will show this year. I also know this because you've been spending the entire offseason, yourself, trying to tell everyone just how mediocre the Bills really are.
With all that said, I expect the Pats to crush the Bills, though.