Mineral extraction of non-renewable resources is a funny thing - when demand moves up, eventually supplies will drop, and prices rise. Then people either find a way to extract energy from a different mineral, or build better technology to remove it from rock, and prices go back down. The drop in oil and gas prices over the last few years being a perfect example of this, as it is due to new drilling techniques.

When the current lull in oil prices ends, electricity will take its place. And we will start the same cycle for batteries that we have lived through over the past 100 years with oil -- either technology will bring out more lithium, or research will move us to use a different fuel source.