Final Fantasy: A Realm Reborn for the PlayStation 4 is now live. In addition, the PS4 Upgrade Function for existing PlayStation 3 players also begins today.
In addition, cross-gen upgrades are also now available via the Mog Station.
Square has advised that you don’t need to buy the PS4 version to upgrade from PS3, although once the PS3 to PS4 transfer is complete, it can't be undone.
To activate the upgrade, you have to register your PS3 build to your Final Fantasy 14 service account then visit the Mog Station to initiate the switch. At this point all of your data will be switched to PS4.