Does anyone know how Tesla will handle a substantial upgrade to the Model S. Some improvement are incremental, like reducing the weight by 200 pounds. Others are easy enough to retrofit, such as software or titanium shields. But there will be others that are significant and too costly for a free retrofit, for example a new battery line with 10 to 20 percent more range. The tricky issue is that Tesla would like to keep the price of the Model S stable over time. But what might that mean as performance improves? Would they price the new line of batteries higher so that price is commensurate with value? If so, then the price of the Model S will get higher over time. Or would they keep the price the same and allow value to increase over time? If so, then the resale value of a Model S will come down as newer versions offer a more compelling ratio of value to price. Of course, in the case of battery improvements, older cars will benefit from the option to upgrade to a newer battery, but their is a nontrivial cost to doing so. Another issue is how to transition. Nobody wants to be the last person to buy the older version at full price. Should Tesla temporarily lower the price of final runs of an older version so that the new version comes in at full price? Or should the new version be temporarily priced higher to smooth over the transition. Basically if you had an order in the works while Tesla announces a major improvement, what options should Tesla give you? You may always have the option to refuse delivery of you older version car, but it would be a very poor customer experience to have to do so and forfeit your deposit. I don't know what the right answer is, but you can see the bind for both parties.