Xbox One Amazon UK page now says orders placed after November 13 may not arrive before Christmas. The PS4 Amazon UK page offers the following notes:
"Customers who pre-ordered this console from August 7 up to and including November 13 will receive their consoles before Christmas. Customers who pre-order this console from November 14 will receive their consoles after Christmas."
Amazon's North American next-gen pages don't offer any warnings about holiday arrivals, but they also don't offer pre-orders at all. Amazon's Xbox One and PS4 pre-orders are closed at the moment, though it's worth noting the PS4 launches tomorrow, and the Xbox One on November 22.