If you want to start playing certain games on the PS3 prior to getting your hands on the PS4, you can do so according to an announcement made by PlayStation at gamescom earlier. According to the announcement, if you buy a supported game (including Assassin’s Creed IV Black Flag, Watch_Dogs, Call of Duty: Ghosts, Battlefield 4, and NBA 2K14) for the PS3 prior to a specified date, you will be given a code that will allow you to digitally upgrade the game to the PS4 version through the PlayStation Store. This upgrade is not free, but does come at a significantly reduced cost: $9.99 ($14.99 for NBA 2K14). This seems to be a good deal for those who want to get in on the action of these games prior to the release of the PS4.
The program is only valid for a limited time, so if you want to take advantage of it keep track of the dates. For Assassin’s Creed IV and Watch_Dogs, you need to have purchased the game and redeemed your code by January 31, 2014. Similar rules apply for Battlefield 4 (March 28, 2014) as well as Call of Duty: Ghosts and NBA 2K14 (March 31, 2014). You can redeem the code prior to having a PS4 so you won’t be hindered by the expiration date if you buy the game within a reasonable time. Instructions on how to redeem your digital PS4 version can be found here. No official word yet on if game saves will transfer from PS3 to PS4 versions, but it seems likely that you would be able to access the save as long as you are using the same account user ID.