They're still plugging away. Turn on Halo: The Master Chief Collection today and you'll find a 1.6GB patch awaiting you. It tweaks some minor details, from rankings to matchmaking, but that's not the reason to read the patch notes - we're more interested in a little addendum at the bottom of the page:
"We’re excited about the progress of the Relic multiplayer map remake and the Campaign for Halo 3: ODST, both of which are on track to release within Halo: The Master Chief Collection next month with our next content update."
We've known Halo's much-loved jazzy side-project would be arriving soon - and at no cost to anyone who played between release and 19th December last year - but this is our first conformation of when we'll be able to drop from orbit into those less-than superpowered shoes once more.
There's still no confirmation as to how much ODST will cost for those who played after the cutoff point, nor whether the as-yet-unnamed Halo 2 map remake will be free or paid content.
Between the much-needed usability fixes and ODST - a real bit of forgotten video game history - 343 seems to be doing everything it can to get players back onside after a disastrous first release for MCC. Personally, I'm not sure it will happen until 343 releases a new, flawless experience - I'm guessing there are some Halo 5: Guardians network engineers building up quite a sweat somewhere.