I could see Tesla taking on a similar strategy that Apple does with its incremental hardware updates and iPhones, bumping current models down the line in price as they use economies of scale and engineering advances to put better technology into consumer's garages, while keeping prices constant for new vehicles.
The current Model S, or an extremely similar build becomes the cheaper, mid-priced Model E, while the Model S and X remain at their current and suspected prices, but continue to get the best of the best expected upgrades (AWD in the S, adaptive cruise control, LTE instead of 3G, ventilated seats, increased range, etc.).
The "Silicon Valley" methodology of having the early adopters pay a premium to help raise capital has proven to work on a smaller scale in other industries, Telsa is merely putting this to work in the yet to be seen before auto industry (to much chagrin!).