I don't think natural gas is much of a long-term solution. While cleaner, it's still a process of burning stuff that's been in the ground for eons and increasing CO2 levels in the atmosphere. Plus, recall that only a few years ago the price was rising rapidly, in no small part because of lack of pipeline capacity in the US. Natural gas has a low energy density, so you either need to compress it (meaning high pressure tanks are needed), or liquify it (adding additional costs and storage issues). It's great for trucks, but not so good for traditional cars.
I think natural gas will be increasingly used as a transitional fuel, but I hope we don't think that it'll let us keep our "Happy Motoring" (TM-Kunstler) mentality.
Cheers,
Scott.