Holy wow. This is everywhere. Without reading these articles, I'm speculating: 1. Bungie wants to move on from Halo. They've had a great time, but they know Microsoft's tendency to beat a dead horse. So they're out. 2. Related to point 1, they want to try something new. If you look at Bungie's history, they used to develop Mac games, then they moved to PC, then they moved to Xbox... at the same time they moved from FPS to Strategy to FPS again. Microsoft might not give them the freedom to try something else. 3. Surely they'd be taking in a bigger cut if Microsoft wasn't taking loads of the money from Halo 3. I don't think (and I hope) Bungie's people aren't really like that though.
So what will they do next? I think they'll continue the other Halo projects, including the mysterious Peter Jackson stuff, and the possible movie. But as to their next major property?
I think they'll make a huge MMORPG that is less open ended than WoW and more story based, and then release it on the new Amiga OS. Sound possible? Clearly, the time has come for Pimps at Sea.