The Bills are currently 16th in the league in average attendance per game, ahead of teams like New England, Indianapolis and Pittsburgh and right behind Seattle.
http://www.espn.com/nfl/attendance
I would do what a number of teams have done: lower capacity to around 64,000 in a nice new open air stadium and charge a bit more. Create a demand for tickets.
Chicago's stadium holds 62,000 fans. They're a tad bigger market than Buffalo.