The upcoming Master Chief Collection update focuses on ranking, title-specific improvements, as well as systems that address quitting, betrayals, reputation, and more.
— Halo (@Halo) April 4, 2015
You can find the full details of the upcoming update here, which also talks about Halo 5's somewhat mysterious Hunt the Truth initiative. There's no new information, but if you haven't been following it closely, it offers a nic refresher.
Finally, the update says, "Over the next few weeks, we’ll start talking a bit more about Relic, ODST, and future updates. We’re excited, and we hope you are too." Hopefully we'll have an ODST release date soon.
[Source: Halo Waypoint]