From liveblog of today's London store opening:
20:45. Question: When do you feel that there will be a time when the Tesla is more accessible to the mainstream market?
20:45. Answer: “About three years (isn) we will get to a mass market, affordable car. About half the price of the Model S. It’s not that we don’t want it less than that. It’s what we think we can achieve.”
20:46. “It’ll take another generation, three years after that, we’ll get an even more affordable car.” — Ed: Essentially this means Tesla is working on a more affordable car after the Model E.