Sony has confirmed that First Light will be arriving on the PS4 as a standalone DLC on August 26th.
Posted directly on the PlayStation Store, Fetch's story will expand further for $14.99. You can read the announcement below in the original story.
Original Story (6/10/2014):
Sony announced Infamous: Second Son's first DLC titled First Light and it puts players in the shoes of Fetch to learn more about her story.
In a tale described by developer Sucker Punch's Jason Connell as "heartache, drug abuse and abandonment", Infamous First Light aims to explain why Fetch is who she is when Delsin Rowe meets her in Second Son.
Taking place in Curdun Cay after being captured by the DUP, Fetch's story brings her to new locations as well as the familiar Seattle. Second Son allows players to use some neon powers from Fetch but as we will soon find out, she has her own unique way of using her own powers.
First Light will be available in August for PS4.