From Michael Mumbauer's (former Studio Head/Senior Director of Visual Arts) LinkedIn:
>His latest achievement is having built a brand new, all-star, AAA Action/Adventure development team for Playstation. Based in San Diego and utilizing proprietary engine technology, **this team was assembled to expand upon existing franchises** and craft all new stories for the next generation of gamers.
This team is working with another Sony studio on an action adventure game. There were already speculation this was Uncharted, and this solidifies it.