I did find that the Power Dollars does currently expire on the 2nd of January, but I'm pretty sure you also have to actually take delivery as well!
So be very careful that your dealership isn't playing you in such a way that you get trapped into a situation where you're locked into a deal where they closed before year end, but then can't give you the Power Dollars because of delivery beyond the 2nd.
They'll claim that they can't control FCA rebate policy, which is true to the best of my knowledge.
You'll come out on the short end of the stick and be locked into a deal with a missing trade in.