We'll see a $30,000 model from them in 2015, and then a sub $20,000 model by 2018, with reasonable mileage. By then the country should also be covered with their solar-powered superchargers, that charge the cars for free. All of these factors should help them, and EV's in general, to become mainstream by 2020.
In regards to the author's last statement, when Tesla started pushing for Tesla Roadster I also thought they would eventually become the "GM of the new electric car industry". Tesla is the Apple of EV's, and GM is Nokia. And both incumbents were gigantic at first in their own markets, compared to the new entrants, but that quickly changed in a few years.