Hi Occitan,
Just think a minute, in 1908 what was the per capita electricity production capacity in US?, I would guess only a fraction of the 11,000 kwh today. Now that allows a lot of todays electricity to be diverted for trams, electric cars etc. Most developed countries do quiet well with annual 4,000 to 8,000 kwh/ per capita.
In the US 15 million new vehicles are sold per year and 50% of VMT is done by vehicles aged 6 years or less. By 2010 there may be less than 1million hybrids sold in US, but many other vehicles having much higher fuel economy than existing new cars(25-27mpg) could be sold, and if gasoline stays above $4 a gallon will be sold. SO in 6 years we could have 50% of VMT by vehicles perhaps having 50% or possibly having 100% better fuel economy than todays new vehicles. your assumption that it would take 100 years to replace entire vehicle fleet with hybrids is assuming that the maximum production of hybrids will never exceed 7% of market. If think even GM completely changes it's production in less than 20years( look at how quickly SUVs and light trucks went from 10% of fleet to >50%). At the rate of new SUVs sales could see SUV and light trucks back to 10% of new fleet in a few years. Since this segment has 22mpg average fuel use, if these were replaced by 44 mpg vehicles, very substantial reductions in gasoline use would be possible.

If you look at traffic on weekends, its obvious that a lot of VMT are not essential for work or for the productive part of the economy, but are for shopping, entertainment,recreation. If prices continue to rise to say $8 a gallon( European prices) or even higher, 2 car families will use the more fuel efficient vehicle more often, a even cut back on some driving.We will probably see an increase in mass-transit use.

I like the idea of mass-transit but its just not going to happen very quickly because of the very high capital costs, the way cities have been built since 1945 and great increases in taxes needed. Much easier to convince US (and Australian) public to buy new plug-in hybrids and hybrids and save a bundle on gasoline, keep the suburbia dream, add a little insulation to homes, replace incandescent bulbs with more efficient lights and a few other token conservation measures .