By the time electric vehicles make up the majority on the road, electric power will be different in significant ways. One vision for a grid of the future is that every (or most) homes have solar, and charge batteries, then sell to the grid based on instantaneous market price. This is a losing proposition today, but with improved batteries, could happen in the future. A power blackout would affect a much smaller area, as generation would be distributed, instead of localized at one big power plant, where any break in the lines could wipe out a whole city.
Large area impacts such as hurricanes affect gas cars, today, but when the roadways clear, people can drive long distances to get gas. By the time we have the majority of cars electric, an electric car will have a long range, too.
This is the same kind of question that someone might have asked in the early 20th century, when "car" still meant "carriage," that is, horse-drawn. When the majority of vehicles are gasoline-powered, how will they fuel up after a disaster, if the only station in town is wiped out? After all, we can get oats for our horses anywhere, and even without that, hay, or just wild grass. The answer was, the world will be different by then.