Fuel prices in general are not going to fall much from todays levels (as we move closer to the banning the sale of petrol cars) reducing the use of hydrocarbons in general and oil producing dependant economy nations will reduce production to meet falling demand to maintain revenue streams for as long as possible.
Gas guzzlers may also fall out of fashion, we may see more of a downward pressure on their values, as we experienced during the '73 oil crisis
Obviously if the annual mileage is pretty low it maybe an acceptable cost owners are prepared to bear, but other environmental factors may come into play such as more restrictions on where and when such cars maybe driven and the availability of components for modern engines.
We are looking at selling our Morgan Roadster (for different reasons ie going down to one garage) but would in a few years time consider a Morgan Plus 4 automatic as our only car (once long term reliability has been established) as both the wife and I can then drive it.