Not sure where you are, but hopefully we try harder to move away from cars in the US and adopt more rail (light, high-speed long distance, etc.) so in that world, they get replaced with housing or literally anything else.
Gas stations are almost all hazmat sites. The underground tanks leak and years of spills accumulate. They will need to excavate and remediate before housing could be built on the sites.
The big brands are doing that. In my area, Mobil remediated the sites and sold them off.
Railways take 10-15 years to plan and build, so unless they are in play right now I highly doubt you will see anymore in the future
Rail isn't gonna do anything to help suburbs and rural areas. Nor even cities, if they are spread out like LA.