The good news is that as the price of oil keeps escalating, alternative sources will become more economically attractive. But let's face it, if alternative sources really and truly begin gaining momentum, the gas & oil industry will fight back hard. I can't imagine that they will sit and watch their multi-billion dollar revenue stream dry up. Won't surprise me if they announce new techniques and breakthroughs within the next few years that will make oil production even more cost effective that will allow them to justify a significant price drop to put financial pressure on the profitability of the alternative energy industry.
I think a more realistic long term source for us will be nuclear energy. Instead of putting gas in your car, you'll recharge with electricity. This new demand will require upgrades to our national power grids which will mean construction of more nuclear plants.