From the IMF blog, a great chart showing the rate at which motor vehicles took over from horses early in the 20th century. Putting current motor-vehicle and electric-car use on the same graph makes a pretty good visual case that we might be as little as 15 years from the cross-over point where half the vehicles on the road are electric.
Greater affordability of electric vehicles will likely steer us away from our current sources of energy for transportation, and toward more environmentally friendly technology. And that can happen sooner than you think.
Source: Chart of the Week: Electric Takeover in Transportation | IMF Blog