It wouldn't surprise me if the Dolphins were to miss the playoffs next season. For one, they'll have to play a first-place schedule instead of a last-place schedule. Also, Parcells' teams have been known to exceed expectations in Year 1 and fall back a bit the second (see his time in Dallas as an example).
As for the rest of the division, the Jets aren't that big of a threat -- especially if Favre sticks around -- and the Pats are the Pats.
If the Bills can actually get a coaching hire right for a change (an Everest-sized order, I know), they'll have a chance to compete.