Even if all cars produced today went electric your probably looking to at least 20 years before gas powered cars wear out and are off the road.

Currently buying new off the lot gas powered cars won't be banned in California until 2035. If we are optimistic and car manufacturers switch over to electric by 2030 then the last of gas powered cars will be going off the road by around 2045-2055.

Most people born today will still start out using gas.