Will PS4 ever play PS3 games?

If you're referring to PS3 BD games, no - Sony has announced repeatedly that they have no intention of making the PS4 backwards compatible with PS3 disks, in large part because the PS4 requires a lot of horsepower in a small package. There's not enough of a reason to make it backwards compatible, and doing so would significantly raise the cost. That's the lesson they learned with the original PS3's, and the reason that subsequent PS3's weren't backwards compatible.

The other reason is simple - money. While you won't be able to play PS3 disks on a PS4, they will be available as DLC's. Sony has been doing that on PS3 with old PS1 / PS2 games, as part of their Classics series of downloads.

Lacking the PS3 specific hardware I don't see it happen soon. Look the PS3 has some really custom hardware, its CPU is definitely not something easy to emulate and so the list goes on.

Hell it is hard enough to emulate PS2 games. The PS3 cell processor is allot more special!

But Sony bought gankai, a streaming service, so what is possible is that you can play PS3 games through streaming. That means Sony Servers will run the games and you get the game streamed your way.

It took Sony quite a while before they made PS2 games run well on the PS3. That is after they removed the PS2 hardware out of their SKU's of course. You now can buy games like GTA: San Andreas but it certainly took a while..think 5 years into the generation.

So don't expect a day one patch to play PS3 games.

@raven

The PS4 IS more powerful then the PS3, the reason why it isn't compatible is because the PS3 uses a very different types of CPU. Emulating the PS3 Cell on the PS4 would be pretty though to do.

So yes the PS4 has more power BUT it lacks specific hardware..like the PS3 Cell Processor to make PS3 games possible.

Yes there will just like the PS3 did like maybe 2 years ago n the first models ps3 was backwards compatible but nobody knows if it will start off with it being backwards compatible from the start with the PS4

no same think with xbox cant play 360 games on the xbox 1