I saw an interesting program on PBS about a month ago on the future of cars and it seems like most of the big car makers (GM, Mercedes, etc.) are planning to roll out hydrogen fuel-cell cars within about 10 years time. Though usually you can count delays, it's amazing how far hydrogen concept cars have come so I would expect them to debut enmass 10-15 years from now.
The debate among the automakers seemed to be about how to package them, either looking like the current combustion models but upgraded to a fuel-cell or futuristic looking concept cars, designed to take full advantage of the technology.
