It is a good question. The question is whether we will have more cars because we make it more economical or easier to own cars. There are a hundred ways to limit the number of cars that people drive. Should one be that fuel is too expensive? I think the answer is no.
What we need to do is make vehicle ownership reasonable for those who need to own vehicles, because certainly a lot of our infrastructure today is built up around owning cars. I live in the suburbs, and if I look at life without an automobile, my quality of life would go down an awful lot, just in trying to get around. Even using public transportation in the suburbs is difficult because of timing and the distance to bus stops and the cold weather, etc.
I think we need to make owning a vehicle as simple and reasonable and inexpensive as possible for those who need it. If we need to limit cars, that should be done another way, not because of fuel prices or because of something that's out of our control.