I remember reading an article (a little after Halo 3 was released) that Jason was working on something new. This bit of information involved an interview with Harold Ryan. The game's been in concept stage for quite a while. As for his contribution to Halo. That pretty much ended with Halo 2; aside from general feedback he offered designers afterwards. Staten too had less of a hand in the development of Halo's main storyline after Halo 2. He had almost nothing to do with Reach's storyline and had less to do with Halo 3's plot than Halo 2. [Edited on 11.27.2012 9:28 PM PST]