I think people overestimate the impact of expensive gas. At $4.50/gallon, my wife and I spend $300-$400/month now (no SUV’s in this family). At $9/month, that will double, but it’s not that noticeable when we easily spend $1k+ on groceries and eating out every month for the three of us (incl. baby).
Expensive gas has had virtually no impact on us, other than to make us pay more attention to how we use it. No change in our plans to live in the burbs. It doesn’t take much in the way of sacrifice for a middle class family to eek out an extra $400/month for gas, if they’re smart with the rest of their budget.