I would let them stew on it for a while. They've already showed their hand telling you they are willing to come down in price. You may not get it for 10,500 but guaranteed you won't be paying full price.

The last pickup I bought was a 2 year old trade in that was exactly what I wanted. After a test drive I offered way less out the door price and after the "I have to ask my boss" game they accepted my offer. The moral is, they have to know that you are willing to go elsewhere and spend your money. Waiting until later in the month is solid advice, I would say give it a week or so and then contact them to see if they have reconsidered your offer.