New Game Plan, For ps4 and ps3

Today at Sony's Gamescom 2013 press conference, Sony announced that gamers that buy Battlefield 4, Assassin's Creed IV, Call of Duty: Ghosts, or Watchdogs on Playstation 3 will be able to buy the digital version for Playstation 4 for a "significantly discounted price" once it becomes available, presumably when the PS4 launches on November 15 in North America.

Although not stated explicitly, this program seems to be a direct response to GameStop's promotion that allows gamers to trade in their current-gen versions of games to get them on next-gen for just $10 more.
EA, Activision, Ubisoft and Warner Bros. were named as partners in this program. Presumably more games will be announced as part of this digital upgrade program in the coming weeks.