The last time gas went up, I saw more people selling their boats and PWC than biking on Long Island. Public transportation did report more users, but service is terrible given the population. Unfortunately, the transit infrastructure here is about getting people in and out of NYC rather than across the island and since the place is a giant suburb, few people make sensible choices regarding where they live relative to where they work. Even if gas went to $10/ gallon, there would be MANY more cars than bikes around here...
That said, I know lots of people who ride 6 months a year and extend the season depending on gas prices. However winter weather and early darkness compound to make a lot of cyclists very uncomfortable at this time of year so even though gas prices are in the $3.30s right now, fewer people are riding than would be riding if it were April.