I contacted Starbreeze CEO Johan Kristiansson through e-mail, and he informed me that
"We are certianly working on it, and we are almost done actually and the game looks great. We are just waiting for the marketing campaign to get started now."
He didn't give me a time frame for release, but it seems like it will hopefully be out sooner rather than later.
The Chronicles of Riddick: Assault on Dark Athena includes the full single-player campaign from Escape from Butcher Bay along with a brand new single-player campaign as well as brand new multiplayer modes. It is coming out for PC, PS3, and Xbox 360 sometime this year.