A Russian Quantic Dream fansite has found what appears to be the LinkedIn accounts of two former scriptwriters who worked on multiple unannounced Quantic Dream projects.
Both of the writers worked with the Heavy Rain developer from 2012 to 2014; one lists in his credits "unannounced Quantic Dream projects" for PS4, while the other lists a single unannounced project from the studio. It's unknown if they worked together on the same project or projects.
The pair also worked on the upcoming Detroit: Become Human (shown) and Beyond: Two Souls.
[Source: Quantic Dream Games Fansite]
While the LinkedIn accounts of the writers appears legit, it's hard to know if these projects would ever see the light of day, how big they are, or if they're still active. David Cage has been known to talk about ideas that aren't yet fully formed games – like in the instance of the Kara and Dark Sorcerer tech demos – so it's hard to tell if these projects are actual games or not. Perhaps we'll hear about these at E3 in June.