Elon Musk has taken to Twitter to tease a new media event for March 19, where a new OTA software update will "end range anxiety" for the "entire Model S fleet".
Tesla press conf at 9am on Thurs. About to end range anxiety ... via OTA software update. Affects entire Model S fleet.- Elon Musk (@elonmusk) March 15, 2015
Normally hardware upgrades have been the catalyst behind improved mileage, but an OTA software update is much more interesting. We could also see the official rollout of the "torque sleep" update, which will allow the P85D and 85D dual-motor vehicles save energy when you're foot isn't on the throttle.
Musk has said that all Model S cards will get the update, so we'll have to wait and see what is unveiled at 9am on Thursday morning.