Car manufacturers are trying to stop using Nickel-Metal-Hydride batteries because they are heavy and to maximize battery life, they only allow the batteries to charge up to 75% and discharge to 55%. Also, the price of nickel is going up pretty fast. Lithium ion is more promising because it's lighter, has a longer battery life and can hold more power while taking up less space...But they cost almost twice as much as Nickel batteries.
I'm not pessimistic about it, but the way I see it is that hybrids barely reduce fuel economy or emissions, and one way or another, as much as I hate to say t, we will eventually have to get off of fossil fuels eventually--be it in 10 years or 100 years. I think that there are some other more promising, permanent alternatives such as hydrogen, pure electric and possibly ethanol.