Friedman is certainly experienced when it comes to writing Cameron's characters, having served as writer and producer on Terminator: The Sarah Connor Chronicles. His other credits include 1996's Chain Reaction starring Keanu Reeves, Steven Spielberg's War of the Worlds, and the crime thriller The Black Dahlia. He also worked on the 2011 TV pilot adaptation of Locke & Key.
Cameron has been working on developing the sequel(s) to Avatar since the original's record-breaking run in cinemas, with the second movie reportedly set to explore the oceans of Pandora. Sam Worthington (Jake Sully) and Zoe Saldana (Neytiri) are confirmed as returning, along with Cameron regular Sigourney Weaver (Dr. Grace Augustine).
Update: According to Variety, Cameron has also brought in Shane Salerno (Savages) and the duo of Rick Jaffa and Amanda Silver (Rise of the Planet of the Apes), who will join Friedman in working on the scripts for three Avatar sequels. Apparently all three will be shot simultaneously, with Avatar 2 arriving in December 2016 followed by Avatar 3 and Avatar 4 in 2017 and 2018 respectively.