As with the Playstation 3, the next generation console from Sony will support keyboard and mouse inputs via USB and/or Bluetooth. Whether or not you will be able to use these peripherals within a specific game is solely dependent on the game itself. You can usually find compatibility information printed on the packaging.
According to DICE producer Aleksander Grøndal, the developers of Battlefield 4 are open to mouse and keyboard support on Playstation 4. This topic was briefly discussed when talking with AusGamers.
AusGamers: Now I’m not sure if anyone really talks about this, but native mouse and keyboard support was available for the PS3 if developers implemented it. I’m not sure about the PS4, but is that something you guys think about? Is it just baked into the product anyway?
Aleksander: We have mouse and keyboard support for the PC obviously, but I can’t speak now specifically for next gen consoles. But if it makes sense in the Battlefield universe, for a Battlefield game, we’ll consider it.