I personally think it would be better for the Bills if the Dolphins went into rebuild mode. That's another 2 or 3 seasons, at least, of them not being a contender, most likely. They have the ability to be a pesky team as it stands right now.
On the other hand, a rebuild means there is a small chance that they get it right.
I want our divisional opponents to be rebuilding as much as possible, though. Rebuilding teams usually suck.