You can't wait until generation is cleaner before you start developing electrical vehicles.
Also... not everyone lives where coal is king. Think of electric cards in areas with high wind penetration. There are places where the variability of wind power (combined with high penetration) causes short-term gluts of power. A smarter metering system targeted at those cars could provide plenty of cheap and clean power.
Obviously areas with high hydro/nuclear penetration don't even need "smart" metering.