The only chance of a better price is if they later revise the price down as the car accumulates months and miles.
The drawback is someone may buy the car before the price is adjusted down.
Totally agree with @Boourns about timing. If time is on your side, keep an eye on prices and wait. Sometimes you will find better pricing towards the end of the quarter.Also, many feel sooner or later there will be a Model S update/refresh and when that happens, current inventory will likely be additionally discounted.
So any price adjustments come from Tesla, not from you. With the price they offer you, there is no further adjustment.