Not only will PS3 games not carry over, but neither will any PSN game purchases or game saves.
However, all is not lost. Technically there are a variety of ways that players could still access their PSN games. Through the PS4's the cloud service or Gaikai's streaming service, this would be made possible. Unfortunately there's a catch, Sony has to choose to implement this service.
Shuhei Yoshida, President of Sony Worldwide Studios, put it bluntly in a roundtable that the company are undecided on the matter. He also mentioned the issue of how different the PS3 to PS4's insides, and are trying to avoid draining the systems power with emulators.
At Wednesday's conference David Perry, Gaikai CEO, said Sony wants to eventually make the PS4 backwards compatible (for PS1 games and beyond) using Gaikai based-streaming. With that in mind, it would be a good step for Sony to at least start with honouring PSN purchases. Here's to hoping Sony will do the right thing, but don't be surprised if it doesn't happen.
But when it comes down to money (as this is a business) there are some reasons Sony would choose not to do this. Truly, users will re-buy their favourite titles to play on the PS4. Much like re-buying SEGA Genesis' games on the Xbox marketplace, it's common to buy older games on updated consoles, and the company makes additional cash. Though some grumble along the way, the fact is, people have re-purchased games multiple times over.
With matters almost settled on the backwards capability of the PS4, or lack thereof, is this at all affecting your decision of buying the PS4? Let us know in the comments below.