A shame, I would much rather we started moving towards hydrogen and electric cars. Even with this process I imagine the the exhaust still causes massive air pollution.
Those would require nuclear power to generate clean electricity, the prospects of that are pretty dim. I don't think burning natural gas derived gasoline would be very polluting, CO2 would be the main concern. It's probably better than burning coal to generate electricity, since with coal all the energy comes from carbon, where with NG and oil you're also burning hydrogen. With electric cars you also have to consider the environmental impact and energy cost of building and replacing all those giant batteries. Probably hydrogen fuel cells are the better solution, but still you need a clean way to generate electricity, and there's no hydrogen infrastructure currently.
As far as running out of natural gas, big new deposits are coming on-line all the time in the US and elsewhere, thanks to the new methods of production that have been recently developed, so I don't think it's going to run out any time soon. Probably the small, modular nuclear power plants are the long term solution, or may be if they ever get fusion working, but we'll see.
Edit: By new methods of production I mean fracking: http://news.yahoo.com/s/ap/20110612/ap_on_...ling_boom_towns