Digital PS3 games won't require a code to upgrade to PS4, but they will require the actual next-gen console. On the PS4 PlayStation Store, next-gen versions of that account's PS3 games will appear discounted to $10. Sony previously said the upgrade price would be determined by publishers.
Check here for a step-by-step rundown of the retail and digital redemption processes. Games enrolled in the upgrade program are Battlefield 4, Watch Dogs, Call of Duty: Ghosts and Assassin's Creed 4: Black Flag.