As announced during PlayStation’s Gamescom press conference, there will be a simple way to upgrade to the PS4 digital version of four select games, for a low discounted price, when you buy the PS3 version of those games.
Assassin’s Creed IV Black Flag, Call of Duty: Ghosts, Watch_Dogs, NBA 2K14 and Battlefield 4 are the supported titles for this program. When you buy the Blu-ray Disc or digital version of these select PS3 games, for a limited time, you will receive an entitlement to download a PS4 digital copy of the same game from PlayStation Store when it becomes available, at the discounted price of £9.99/€9.99 (or £11.99/€14.99 for NBA 2K14).
Full details on PlayStation Blog