It's very much like buying anything. You could buy today and find the item goes on sale tomorrow or next week. The way you need to look at it is what price are you happy to pay. If you get a price you're happy with, order the car and then try your best to turn a blind eye to whatever deals come out next week or month.
Perhaps look at sites like Carwow to get an idea of what prices you can get and then go to your local dealer and negotiate with them. Also, if you're not wanting extras, perhaps consider a pre-reg.