People shop on Black Friday. If I don't have a sense for the Nexus release, I am probably going to pick-up the RAZR - maybe not Friday specifically, but some time next week. That's when a lot of people do their shopping, and buying gifts. People are off work and have time and probably a good number of people sitting on upgrades who will use the time to pick-up a new phone (like myself).
The average or typical user is not going to care or know to return a RAZR for a Nexus after unwrapping on Christmas. Lots of phone will be sold next weekend and if the Nexus isn't in the mix it will lose a lot of sales.
I just don't see a several hundred dollar cell phone being high on the xmas shopping list, (at least not in this economy) maybe a flat screen, PC, or a tablet, but not so much a phone.
I 100% agree that the longer they wait to put the phone out is money they are losing to other phones being sold but as far as losing hundreds of thousands in lost sales because of launching after Black Friday, not happening.