A road or car tax doesn’t have to go away just because the car is electric no? Am I missing something?

As for the fuel tax, why not make up for it with an increase in car tax once sufficient adoption is reached? Once 80% of cars are electric, the car tax increases by an amount required to make up for the average revenue from fuel. At that point, electric cars pay just a high car tax and fossil fuel cars pay both the high car tax and the fuel duty, further incentiveiseing the switch to electric.

Am I missing something? What would be the issues with this approach?