People seemed pretty happy during the Sabres' '05-'06 & '06-'07 seasons.
Same thing goes for the Bills in the early-to-mid 90s.
Give the people something to cheer about, as opposed to a mediocre product, and they'll cheer. I'm pretty sure that Bills fans would rather see the team make the playoffs than see the team go 7-9. Likewise, Sabres fans would rather see the team finish in the upper half of the Eastern Conference, rather than in 9th or 10th place.