Activision and Sony announced that by purchasing the digital PS4 version of Call of Duty: Advanced Warfare players will also receive the PS3 version for free. At the moment, it seems like a similar offer won't be available for Xbox One players.
In addition, players can upgrade their Xbox 360 and PS3 versions to the Xbox One and PS4 versions, respectively, for free. This offer is only available until the 31st of March, 2015. Just like the cross-buy option, this offer only applies to digital copies of the game.
Players will also have the option to carry over the game's Season Pass, Atlas Gorge pre-order map and their multiplayers stats to the other version of the game. This includes both those who upgrade to the next-gen version and those that use the Cross-Buy option.
Call of Duty: Advanced Warfare launches worldwide for PS4, PS3, Xbox One, Xbox 360 and PC on the 4th of November. Those that pre-order the game will receive the Day Zero edition, which allows players to gain access to the game a day earlier.
Source: Playstation Blog