http://en.wikipedia.org/wiki/Tesla_BlueStar
2015 would be on track for the Bluestar, but I remember Musk saying this year that it was basically delayed until 2017, which was pretty disappointing. I wonder what changed.
Either way, $20,000 Tesla in 2018 then? It would follow Tesla's strategy of releasing a new car every 3 years that costs half as much as the previous one. Even a $25,000 one would be very nice. If I were them I'd try to make it my goal to have a $20,000 car by 2020 (like those nice renewable energy goals).
I think in the 2020's electric cars will become mainstream, and most new sold cars would be electric, due to the mainstream price-point they will reach, and the mainstream-level mileage they would get by then.
According to Musk batteries improve the capacity (at the same price point) by 5-8 percent per year, which is a little slow, but still great news for electric cars in the long term, considering they can get batteries for half the price or double the mileage every 10 years.