the fact is there aren't that many larger markets
Who is significantly larger then Buffalo and its suburbs and doesn't have a team ??? When you include southern Ontario Rochester, and Buffalo and its suburbs we are a decent sized market.
http://www.infoplease.com/ipa/A0763098.html
there are a few options but most of the options are already close ot existing teams, or are more of a college football cities.
A new stadium with better boxes would help, and ticket price increases are coming.... but if we can meet those requirements I think there is a solid chance Buffalo can keep the Bills for a long time...