Elon Musk recently announced the latest software improvement on Twitter (embedded below) for the Model S to make the P85D even quicker. The upgrade sheds a tenth of a second off the dual-motor's already impressive acceleration to 60 thanks to an improvement to the inverter algorithm. The tweak affects the single-motor P85 too, but Musk said the effect would not be as significant. We can't wait for the inevitable updated passenger reaction videos once this enhancement tweak goes live.
P85 acceleration will also improve, but not quite as much- Elon Musk (@elonmusk) January 29, 2015