Even the most rosy predictions put peak oil at 20 or 30 years away, so it's definitely something to be concerned about. The thing is, it will take 20 years or so just to make all the infrastructure changes to ensure a smooth transition away from a petroleum based economy.
It's not just gasoline that is an issue. Almost every aspect of life uses petroleum products in some way. Plastics, tires, dyes, nylon, liquid soap, insecticides, fertilizer, rubbing alcohol, some pharmaceuticals, and much more - all are petroleum products. Almost nothing about modern life would be the same without petroleum.
Also, I don't think most suburbs are going to see much light rail. Most of them just don't have the population densities. A few more buses would be more likely.