Cost reduction and efficiency improvement for electric vehicles are limited. Electric power production costs aren't going to change much, nor is the cost of making vehicles, except for quantity discounts, because they're basically the same as internal combustion vehicles.

There is no chance of improvement in electric motors which are already up in the high 90% range. So that leaves battery technology as the only real leverage.

Unfortunately the United States and Canada are rather low in lithium reserves so we'll end up with a dependence on foreign lithium. Fortunately neither China nor the Arabs are leaders here. Bolivia, Afghanistan, Chile, Argentina and Australia are the leaders, Chile, Bolivia and possibly Afghanistan by a wide margin.

Of course, if we maintain Afghanistan as an occupied tributary state that could assure a low cost supply.

There's always the possibility of a breakthrough in battery or fuel cell tecnology - but none seems known right now.