Its simple supply and demand. If the production of gasoline powered cars ceases, then the retail demand for gasoline will decline over time as the last gas cars wear out and oil companies would leave the declining retail gas market to invest in more profitable markets. Some oil companies may even cut their losses and put out of the gas station market early.Anything the collective they can do to drive the cost of living through the roof and screw the every man over, that's what I expect. Time will tell.
Most likely gasoline will still be produced and sold to the commerical market like avation and Ag, but still could become difficult for the normal consumer to purchase. Basically gasoline could become an expensive B2B product. This is not even considering what BS laws and regulations that may be passed regarding the sale, storeage, and use of liquid fuels in the future.