Mike Morhaime, CEO of Blizzard, revealed that Cataclysm is targeted for a 2010 release date.
Whatever date is up on Game Stop (November 1st, 2010) or Amazon or wherever are just placeholder dates until they start to change or we hear from trusted sources that the dates are correct.
Now a targeted release date should be clearly understood for what it is. It is a date that Blizzard wants to ship their game, nothing more, nothing less. It means that they have a plan and schedule to get the game ready by then. But as everyone knows, long term schedules can and do change.