There is an interesting analysis going around that suggests up to 80% of the world's reserves of Lithium are found in South America (Bolivia and Chile), and that the governments are not keen on being strip-mined of the resource (in other words, they want to process the lithium, not just sell it as a raw commodity which gets exported).
Further, the peak-production point for Lithium looks no more promissing than for gasolene (we may be at or near the peak production for Lithium), suggesting that there isn't enough Lithium to meet projected demand for hybrid cars.
See:
http://tyler.blogware.com/lithium_shortage.pdf for a typical presentation.
So there is still room for a better battery design, if only to combat the uncertainty over Lithium.