Through the end of the year, Square Enix will allow PlayStation 3 users to upgrade to the PS4 version of Final Fantasy 14: A Realm Reborn for free.
Rather than gaining another copy of the game, those who participate in the offer will effectively be swapping theirs for another. Once character data has been transferred to the PS4 version of the game, the PS3 version will become unavailable. However, this will only be finalized once the MMO releases fully April 14, as it's still in early access. So feel free to cheat the system in the meantime.
To make the switch, FF14 players will need to confirm their PS3 copy of the game and then upgrade their account via Mog Station—again, free of charge.