Now this is all hearsay of course, but isn't Activision '10 kind of the terrible slaver overlord master figure of the games industry? Bungie bought themselves back to freedom ... why? Ostensibly, obviously, probably because they didn't want another party to determine what they can and cannot work on anymore. Entering obligations with Activision now doesn't seem exactly compatible with that direction.
Activision is no better or worse than EA, Bethesda, Square-Enix Eidos, etc... They just happen to have a very vocal CEO that likes to talk to the press. Other than that from a business, developement, and contract standpoint...there's virtually no difference.
Add to that, they still have the rather phenomenal Blizzard partnership. And right now, that's probably the hottest and most bulletproof studio around.
so is this Bungie's last Halo game or can they also still do those?
I'm assuming this is an exclusive publishing agreement for a new franchise (world) that hasn't yet been announced. Similar to how MS basically has exclusivity to the Halo franchise. Except in this case, Activision only has a 10 year window while MS has indefinite exclusivity on Halo.
So, assuming they can field enough developement teams, nothing prevents them from working on another Halo, or any other title not associated with the franchise they are doing with Activision.
Moving to other stuff...
Bungie is possibly a safer bet for another hit title than the former IW heads and team, with a better track record for the past decade+. IW, however, is certainly more proven from a multi-platform perspective, especially in the past few years.
Thing is, has the IW team done anything other than FPS? Bungie at least has done other genres. While ONI may have been a bit of a disappointment. Myth: The Fallen Lords was released to critical acclaim but didn't have an "easy mode" for mass consumer adoption. Game was definitely one of the best strategy games of all time however. And did basic physics modeling well before any games other than simulations tried it...
All my opinion, of course.
If we think of it terms of Activision trading IW for Bungie, I think they came out ahead...
Regards,
SB