Everyone should know enough about the EPA 5-cycle test to simulate the results. Remember that the EPA changed the test right around the time the S was coming out, so the Tesla engineers were estimating using apples only to have the EPA switch to oranges.
Besides, with cars geared for high-end speed, the EPA number isn't going to be accurate anyway. You will likely be driving the car faster than 55 mph so the wind resistance and different gearing will have an impact.
Not always bad either. One car I had had an estimated EPA highway of 25 mpg. If I drove it at 65-68 instead of 55, I got almost 30 mpg. Turns out the engine ran much more efficiently at ~2K rpm instead of 1500 rpm.
If I cruised at 70-75, the mpg dropped back to the EPA number
.
Bottom line, your mileage will vary but not because of Tesla - because your driving patterns have a huge impact on range and the efficiency curves of the D cars are unknown (to us) at this point. You could get lucky and have the curves fit right into your favorite speeds. Or not. We'll just have to see.