Cliff Notes version:

*Transparency is good!
*Dedicated legacy game sustain team within 343, current priority being MCC.
*They're going to be partnering with another external group for MCC fixes and improvements.
*There will be a separate "test flight" version of MCC for testing improvements and fixes. If you're in the Xbox Insider program you can get in on this.
*Beyond just bug fixes, other changes will include:
**Updated APIs to help address disappearing parties, lost notifications, etc.
**Switch from p2p networking fallback to 100% dedicated servers.
**XDK updates for all Halo titles in MCC for XB1X improvements, etc.

All very good news and heartening for people who were afraid that MCC would never get fixed, let alone see meaningful updates above and beyond the original scope.