The problem with that theory is that auto manufacturers face declining average costs and so are incentivized to produce more cars and sell them for a lower unit

The problem with that theory is that auto manufacturers face declining average costs and so are incentivized to produce more cars and sell them for a lower unit price. This is why the only source of auto inflation is by adding more features to the car. I don't see any reason why this would change in the future. For EVs, wait until cheap Chinese EVs flood the US market.