Sony confirmed three of its biggest internal studios are working on PlayStation 4 games at its Gamescom 2013 press conference today.
Naughty Dog, Sony Santa Monica, and Media Molecule are all working on unannounced next-gen titles. Sony didn't dive into any more detail, but it's very likely that the Santa Monica project is whatever Cory Barlog is working on. Naughty Dog said it will retain its Uncharted and The Last of Us engine for PS4 development.
That leaves Media Molecule, which is currently finishing up Tearaway for PS Vita. Whatever it is, we bet it will be crafty and creative.