Tesla's 6.1 software, announced Jan 8 2015, indeed predicts energy usage... although evtripplanner.com shows that you can do so pretty well using map data:
"To help you better anticipate your charging needs, Model S will now calculate the projected energy remaning at your destination using your
predicted speed, the elevation, and other factors along your route. Trip Energy Prediction is only active while using Navigation."
"To help you better anticipate your charging needs, Model S will now calculate the projected energy remaning at your destination using your predicted speed, the elevation, and other factors along your route. Trip Energy Prediction is only active while using Navigation."