Unlike other platforms, PlayStation offered a true cross-buy program where purchasing either the digital PS3 or PS4 version granted access to the other at no extra cost.

The cross-buy and digital upgrade programs for allowed players to own the game on both last-gen (PS3/Xbox 360) and current-gen (PS4/Xbox One) consoles within the same console family.

These were designed to transfer indefinitely within the PlayStation family, provided the same account was used. Xbox Digital Upgrade Details