It's not a question of whether we will convert to a hydrogen economy instead of a petroleum based one, but when. It will be great to see the day when petroleum, coal, and other fossil feuls become unnecessary for every day life.
It's strange to think about, but pretty much all the energy that we harness is essentially solar energy. Plants that took eons to change into petroleum and coal were fueled by the sun. The same thing applies to the corn and sugar cane from which ethanol is distilled. Wind (and hydroelectric, via evaporation and precipitation) is generated from the sun's energy. Geologic and nuclear are pretty much the only extra-solar sources of energy that we are tapping, and they really don't account for much.