Ha ha, I wouldn't read too much into the various team member transitions. Working at a game studio is surprisingly high stress and can be difficult, especially for those with families, in the long term. We spent the vast majority of the last several years working to build up the studio and ship Halo 4. We are in a bit of a quiet period compared to the last couple years and annual reviews and bonuses were completed in early September as they are every year. It's not that unusual for some folks to pick this time of year to step away and pursue other opportunities.
I will miss all of the people who have moved on, not just because they are my friends, but because you form a bond with people that you ship a game with. Especially those I shipped Halo 4 with. I like to refer to 343 as the "great experiment." We literally threw a couple hundred people into a building and said, "make the next halo game." Now, you can judge the results for yourselves (naturally there are things we would have done differently with the value of hindsight or more time) but I will always be proud that we were successful in releasing the game on time.
We learned a lot from Halo 4, and we have brought some incredibly talented and smart people into the studio this year. I certainly can't talk about current goings on in any kind of detail, but I am personally very excited about the future of our studio and the franchise that brought our studio together.