The new Model S 100D is EPA rated for 335 miles. The next big jump will be 2170 cells. That will probably allow about a 130 kWh maximum pack on current chemistries - which would give something in the 430 mile range if the efficiency is similar.
Getting there isn't Tesla's first priority right now, but I'd expect to see it by late next year if not sooner - Tesla probably won't let the press release folks (Audi, Jaguar, Lucid, etc.) out do them.
