I also agree that Tesla won't be able to move gas prices, but there will be a trend for less gas consumption. Apart from a 20k/yr Model S'ses, the competition is reacting as well. In Europe you can buy a 4!!!! cylinder MB S-class, a hybrid S-class and a plug-in S-class will follow soon. Porsche, BMW and Audi have hybrides for their top models as well. Fuel consumption is going down for ICE's as well to prevent the gap between EV's and ICE driven cars to be big enough for people to make the switch.
Gas stations in heavy EV concentrated areas may feel the pain already. Dropping sales will force some gas stations out of business and will make the trip to the gas station an even bigger pain at the rear end as they will be further apart. This will be some time in the future, but I don't think it's a trend that can be stopped.