If you have a binding contract, then no, the price is set. Again, as Kahdir points out, you need to check local laws as not many dealers do this to my knowledge. If it's more traditional, such as a "negotiable upon arrival" or "1st refusal" then you could be subject to any price increases as you would be charged the price of the car as of the day you sign the papers on arrival. If you got a good dealer and they want to keep you coming back, then they'll more than likely honor any presale price they quote you. But get it in writing. Nothing happened if it wasn't written down.
If the car is supposed to be produced in the numbers they want it to be, trust me, you'll get it for any prenegotiated price. They're going to be selling these cars. If it's a specialty vehicle, you may be in for some ankle grabbing. Time will tell.
