Earlier today the release date of the Xbox One on its Amazon.com listing was indicated as November the 30th (as you can see from the cached version of the page). Just now it was changed to November the 27th.
While this should still be taken with a grain of salt, there must be a reason behind the sudden change. Whether Amazon got some information from Microsoft or they just decided to change their release prediction on their own, we can’t know.
One thing is for sure: a November the 27th release date would put the console’s launch in a strategic position just before Black Friday (November the 29th).
The release date for the PS4 is still set as December the 31st, evidently a placeholder.