The Bills have the greater chance of beating the Patriots in the first division game they play against them in the year. Starting from 2003 (to include the Bills last win against the Patriots), here are the scores from the first division game of the year vs the Pats: 2003: Bills 31-Pats 0, (after this, all Patriots victories), 2004: 31-17, 2005: 21-16, 2006: 19-17, 2007: 38-7, 2008: 20-10, 2009: 25-24, 2010: 38-30. With the lone Bills victory in 2003, the Patriots outscored the Bills 192-152 in the first division games of the year. Without that lone Bills victory, the Patriots outscored the Bills 192-121.
Now for the scary part, the second division games of the year vs the Pats: 2003: 31-0, 2004: 29-6, 2005: 35-7, 2006: 28-6, 2007: 56-10, 2008: 13-0, 2009: 17-10, 2010: 34-3. In that span of time, the Patriots outscored the Bills 243-36 in the second division game of the year. In every game since 2003, the Patriots outscored the Bills more in the second division game than in the first.
This shows that Belichek learns a lot from the first division game, and makes better adjustments than the Bills coaches do, which is why the streak has been going on as long as it has been.
The first step for the Bills is to finally get that first victory over the Patriots. The next step, is to be able to beat them in the second division game of the year, when the Patriots have been much better than the Bills in those games.