Gas prices might temporarily fall as there is a very brief over-supply. Then the exact opposite will happen, gasoline will become more expensive as the economies of scale vanishes, refineries shut down permanently (never to be restarted, and no new refineries will be built), the market demand continues to dwindle, and on the cycle goes. Gasoline ends up as a largely niche fuel many decades out.

And that's before we get to the obviously anti-fossil fuel era we're entering, where they will increasingly hammer fuels like gasoline with taxes, driving the cost up around the globe. Even if somehow the market didn't drive the prices up from the economic efficiency change I described, the taxes will regardless and that's guaranteed to occur.