Don't forget the "car charging" business. Tesla announced before that it's willing to license its Supercharger network to other car makers. That business could one day replace most petrol charging stations.
Why wouldn't gas stations merely re-equip with electric charging equipment? They already have the best real estate.
There are also competing standards for DC charging, so I find it highly unlikely that the other manufacturers will license anything from Tesla, rather than settling on another standard.
I'm not sure existing gas stations really have the best real estate. Pulling off the highway for five minutes to gas up is pretty different from plugging in for an hour, and I'm not sure I'd want to do those two things in the same kind of location.