With 5 games left and a 4-7 record, the Bills still have a decent chance to win the division this year. Sure, I'm an optimistic Bills fan, but the most important games left on the schedule are against teams the Bills have already won against (Miami and the Jets) and a team they badly outplayed and will get at home (New England).
I think the most likely scenario is the Bills going 4-1 with a loss to Denver, and New England going 2-3 with losses to Buffalo, Tampa Bay and Miami. It's a longshot, but the Bills can stay in the race until the final weekend as long as they keep winning. They would actually control their own destiny if they beat the Fish Sunday and the Jets beat the Pats. Believe it or not, the Bills could actually win the division with a 6-10 record! The NFL should replace the East division winner with an extra wildcard team if that happens.
Here's a complete list of all the possible ways the Bills can win the division (Hey, fans start getting crazy after a 10-year playoff win drought!)
IF Bills Go 5-0
NE must lose 1 of their 3 division games beside Buffalo
IF Bills Go 4-1 (Loss to DEN or CIN)
NE must lose 2 of their 4 games beside Buffalo
IF Bills Go 4-1 (Loss to NYJ)
NE must lose 2 of their 3 division games beside Buffalo
IF Bills Go 4-1 (Loss to MIA)
NE must lose 2 of their 3 division games beside Buffalo
MIA must lose 1 of their 4 games beside Buffalo
IF Bills Go 4-1 (Loss to NE)
NE must lose all 4 of their games beside Buffalo
IF Bills Go 3-2 (With 3 division wins, losses to DEN and CIN)
NE must lose 3 of their 4 games beside Buffalo
MIA must lose 1 of their 4 games beside Buffalo
IF Bills Go 3-2 (With wins against MIA, NE, and DEN or CIN, loss to NYJ)
NE must lose 3 of their 4 games beside Buffalo
MIA must lose 1 of their 4 games beside Buffalo
NYJ must lose 1 of their 4 games beside Buffalo
IF Bills Go 3-2 (With wins against NE, NYJ, and DEN or CIN, loss to MIA)
NE must lose 3 of their 4 games beside Buffalo
MIA must lose 2 of their 4 games beside Buffalo
MIA would also need a 3rd loss unless they win vs NE
IF Bills Go 3-2 (With wins against NE, DEN, and CIN, losses to MIA, NYJ)
NE must lose all 3 of their division games beside Buffalo
MIA must lose to NYJ and either SD or TEN
NYJ must lose to OAK
IF Bills Go 2-3 (With wins against NE, NYJ)
NE must lose all 4 of their games beside Buffalo
MIA must lose all 3 of their games beside Buffalo and NE
IF Bills Go 2-3 (With wins against MIA, NE)
NE must lose all 4 of their games beside Buffalo
MIA must lose to SD and TEN
NYJ must lose to MIA and OAK