Get your salt shakers, you're gonna need quite a few grains.
There has been no official announcement of this game, but some totally unsourced rumors/"reports" claim the game is set for release in 2017, and will feature one female character, Katherine, alongside a gangster named Irvin, a comic book nerd called Keenan and famous Kenpo fighter Garrett Jr.
The source also claims that Half Life 3 has been "delayed" in order to work on Left 4 Dead 3, just so you know how reliable the report is.