Aka, "Who could make things mildly interesting for the Patriots next season?"
It's hard to imagine any teams in the AFC East making a real push to challenge the Patriots while Tom Brady is still effective, but things could at least get mildly interesting next season. I doubt the Jets will be much of a threat next year, but the Bills at least could make things mildly interesting next year. The Bills defense in particular, which was already pretty good (3rd in opponents passing YPG, 11th in rushing) will make a leap next year under the direction of ex-Jets coach Rex Ryan. The Bills finished 9-7 last year, and with Rex's tendency to get the best out of his players when playing the Pats, they could make things interesting for the Patriots next season.
Their weak spot? Their offense, which finished in the bottom half of the league in both passing yards per game and rushing yards per game. Their defense could be the best in the league next season, but they can't challenge anyone without any offensive game. Even the Seattle Seahawks, who are known for defense, didn't become successful on defense alone. If the Bills want to accomplish more than just finishing above .500, then they'll need weapons on offense.
Make no mistake, out of all the teams in our division, the Buffalo Bills have the best chance of improving and making things mildly interesting in the AFC East. Miami could be a candidate, but they've been consistently so-so the past couple of years and that's not likely to change. As for the Jets, who knows what the future holds? So many questions surrounding that team. Hard to know how they'll fare next season. Again, though, this is all about who takes the jump to making things mildly interesting for the Pats, not about actually challenging for the AFC East crown.