Don't go trading in that PS3 any time soon, because they won't work on the PS4.
While Sony remained quiet regarding the PS4's ability to play older PS3, PS2, or PS1 games during its official event last night, the company has now made things perfectly clear: The PlayStation 4 will not have backwards compatibility built into the system. Speaking with journalists during a roundtable session, President of Sony Worldwide Studios, Shuhei Yoshida laid the out the facts.
"No backwards compatibility. You can quote me on that," Yoshida stated, noting that in the future the console could conceivably accomplish the task through either cloud services or software emulation, but that such talk is completely hypothetical at this point.
The PlayStation 4 - unlike the PS2 and PS3 before it - will not support native backwards compatibility out of the gate. Of course, the PS3 later dropped the feature, so there was really no reason to think the PS4 would be any different. This means that if you want to keep your collection of physical PS3 game discs in your software library, you'll need to hang onto the system itself as well.