Sony recently released an "Ultimate FAQ
" regarding the PlayStation 4. Part of this FAQ includes details on what PS3 peripherals will work on the PS4.
Now while we know that the system won't natively support PS3 peripherals, there's an interesting bit that provides some hope.
Will PS3 peripherals such as fighting sticks and steering wheels work with PS4?
Generally speaking, no. However, at launch, users will be able to use these controllers if a specific game title allows it to be used within the game. This decision is upon the game developer and will vary from game to game.
In other words, if the devs allow a game to use a certain peripheral (probably by packaging drivers and whatnot with the game itself) than it'll work with the PS4.