The canonical reply from Elon Musk on profitability is that they hope to profitable on a GAAP basis in 2020. Let's see if external investors hang in there long enough to allow this. ( http://www.bloomberg.com/news/articles/2015-03-04/as-tesla-g... )
It will be very interesting to see what happens to the used Model S prices now that Tesla took away the buyback guarantee for new cars.