The release date of Pirates of the Burning Sea hasn't been announced yet, but the preorder date has. Starting from October 23 you can get the preorder box at retailers, for which you get a PotBS music CD, a parrot and sword in game, and 15 days of early access with a level cap of 20 to the game. Which is good for people that don't preorder too, because the preorder players will already kick-start the player-run economy.
Do the math: The release date of PotBS can't be before November 7 (15 days after preorder). And they probably don't want you to buy the box and then not be able to use it for weeks. Plus they will want to get the game out before the end of November, for the christmas shopping period. So most likely release date is somewhere around the middle of November. I'm looking forward to it.