The folks at Microsoft did it a while back letting developers use another CPU core and now Sony's doing the same. A recent release of the SDK unlocked a seventh core for developers to use on the PlayStation 4.
Unlike the Xbox One, the unlocked core shares duties between the OS and the game so it's unknown how much this will benefit future games and if anyone's going to take advantage of it.
The funny thing is you didn't hear a peep out of Sony that they did this whereas Microsoft really pushed this when they unlocked a core in their Xbox One.
So, developers will be getting a little more power for their games if they want to use it.