Not regionalizing is not an option for this franchise. Because of Buffalo's small size, its version of regionalizing into Canada is pretty much equivalent to other NFL cities just now starting to market to their own northwest suburbs.
The "Buffalo Bills" is a 50+ year, storied, iconic brand name, steeped in history and tradition. You don't casually mess with that unless/until your fanbase has already gone 60-70% Canadian as a result of other, organic means. I don't think you rebrand in an effort to gain fans, as that would backfire. It's more appropriate to gain Canadian fans then rebrand (way, way down the road, if ever) to better capture the essence of the fanbase.
I believe a Niagara Falls stadium would do far more to attract Canadian fans than a name change would.