Gamers who buy digital copies Call of Duty: Advanced Warfare for PlayStation 3 or Xbox 360 will be granted a free download of the PS4 or Xbox One version, respectively, if they decide to take the plunge and upgrade to the newer consoles before March 31, 2015. Season passes, DLC, and special edition content will all transfer over to the new version, along with any progress you have already made.
Note that this offer does not apply for people who purchased a physical copy of the game, only for digital downloads.
Publisher Activision made the same offer with Bungie’s recent shooter Destiny, providing extra incentive for fans to upgrade to the newer consoles so developers can begin to phase out cross-platform support for the previous generation of hardware.
Details about the offer are available here.