And yet oil probably won't get too much more expensive for decades, while solar is ridiculously expensive without any clear prospect of becoming cheaper (currently parts are only as cheap as they are because the Chinese government is subsidizing their production, which can't last forever). Burning gasoline is not going to stop being economical and reliable any time soon.
Also, given the expensive reality of solar and the way we generate electricity, electric cars would still be getting their electricity from plants which burn coal. Perhaps in 20 years we will be using more natural gas than coal, which at least means we're not depending on the Saudis - but still we'll be using hydrocarbons, fracking, etc.
The only way electric vehicles will become mainstream is if the government mandates this. Seeing the way the Obama administration's "clean energy" agenda has tanked (even among the liberal base preoccupied with drones and Manning), there isn't going to be anybody to support this kind of action when it makes all transportation more expensive and thus makes everything more expensive. In a country which is physically very large, with an economy driven by domestic spending.