While neither Sony nor Starbreeze have yet to comment on it, it seems that the Overkills The Walking Dead PS4 release has been quietly cancelled.
Update: Overkill's The Walking Dead Canceled for PS4, Xbox One
Overkill's The Walking Dead game cancelled - WholesGame
Overkill's The Walking Dead is cancelled for PS4 and Xbox One, PC
Overkill's The Walking Dead Canceled for PS4, Xbox One, PC Version
The Walking Dead News - Push Square
The fall of Starbreeze
A dev build of OVERKILLs The Walking Dead has leaked : r
What canceled video games would've had the most potential? - Quora
Overkill's The Walking Dead is officially canceled, and it's not
The Walking Dead creator open to TV, game crossovers