The Facebook page of Quantic Dreams' Beyond: Two Souls "is hard at work to post their latest artwork project, led by David Cage. The artist behind the artwork is François Baranger. We noticed especially one of his artworks, where he signed with his name an the year 2010. We remember that "Heavy Rain" was published in February 2010. We assume that if Baranger at that time already was finishing the artwork, it is relatively early (perhaps even during the final phase of "Heavy Rain") where the development of Beyond: Two Souls begun.
In fact, the artist noted on his website that he works since 2008 for Quantic Dream on "Beyond: Two Souls". How long the game is finally in development, can only be confirmed by the officials. A look at the works of the artist can never hurt.