Isn't it suppose to be called Riddick 2? I remember hearing that Pitch Black was suppose to be The Hobbit of the franchise, and The Chronicles of Riddick was suppose to be the first installment of a brand-new trilogy. So technically, apparently, the second film would be The Chronicles of Riddick 2: Subtitle.
The Chronicles of Riddick: Subtitle is too long. Why not something simple like Riddick's War?
Or, how about this: Riddick's War: The Chronicles of Riddick: The Origins of Riddick's War.