The high(er) voltage car electrical system is not going to happen anytime
soon. The reasons, according to an article in Car and Driver are a) reliable
circuit protection hasn't been developed to the point where manufacturers
are 100% sure a loose wire or a short won't result in a shock or fire and b)
12 volts is an ideal voltage for headlight filaments- higher voltages
mandate thinner filaments which don't survive bumps and bangs very well.
Apparently GM was going to 48 volts for the 2006 model year, but backed off
mostly because of the circuit protection issue.

-Carl