Sony had announced at their Gamescom 2013 press conference that gamers that buy Battlefield 4, Assassin's Creed IV, Call of Duty Ghosts, or Watch Dogs on Playstation 3 will be able to buy the Playstation 4 Digital Version for a "significantly discounted price" once it becomes available. They also announced that the Playstation 4 would release on November 15th in North America.
Again the PS4 will have a price of $399 and PSN will also be a subscription service, similar to Xbox LIVE. Remember that you will only have to pay for PSN on PS4. PSN on the PS3 will still be free. Gotta compensate for that reduced price compared to that $500 price of Xbox One right?
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.
UPDATE[]
EA has announced how they are doing their upgrade program for Battlefield 4. Inside marked copies of Battlefield 4 for PS3 there will be a voucher with a unique code printed on it. This code will allow you the one-time opportunity until March 28, 2014 to purchase a digital version of Battlefield 4 in the Playstation Store for only $9.99/£9.99/9.99€.
The price for upgrading a 360 copy to Xbox One for BF4 is still &9.99 except that offers will only be valid in the Xbox Live Marketplace until December 31st, 2013! December 31st is also the date at which offers for other stores (Gamestop, Game, etc.) will also expire or until supply lasts. Great to have a PS3 isnt it?
EA has also confirmed that yes your stats and premium membership (if you have it) from your PS3 copy of BF4 will be carried over.