Traditionalists shouldn't get too worried - NASCAR probably won't eliminate gasoline powered racecars any quicker than it adopted fuel injection over carburetors (the last production cars to have carburetors were offered in the late 1980s, but NASCAR didn't switch to fuel injection until 2012). NASCAR will probably allow other fuels (probably alcohol based) before they quit on internal combustion engines altogether. Unless NASCAR remembers that it was started with cars that were based upon currently offered production cars...
Charging electric cars will be a challenge, but it is achievable. There will be better use of power produced at night - most power plants are not throttled down when demand lessens at night (so power is wasted as heat in the wires and equipment), while many electric car owners already recharge at night while they are sleeping. The power grid is upgradable, and there will be time to do it because of the slow rate that electric cars are catching on. Not all greenies are against nuclear plants - there are new designs that are less dangerous (although disposing of used fuel rods is still a problem). Alternatives like solar and wind are getting better. Also, people do not have to charge by using the power grid if they install their own solar panels.
Will the fans like electric car races? Probably not at first - especially the traditionalists, who will miss engine noise. They will hear tire squealing, and probably some kind of low electric motor / electronics noise... they will probably be able to actually hear the announcer (so he'll have to stay on top of his game - and I hope tracks don't get ridiculous about playing commercials)... they probably won't have to outfit their kids with earplugs. The blow-by / vibration that you feel if you are close enough will still be there (without the exhaust component).