Halo Master Chief Collection seems to be in the last period of official support as Microsoft aims to focus on Halo Infinite when it launches.
Halo MCC is looking at the eighth and final season of its live support as per 343 Industries announcement. The developers stated they want to make it one to remember since the decision to hang up on the seasons is indubitably going to cause controversy.
While the teams handling Infinite and MCC are separate entities, they do interact in several aspects, mostly revolving around live services, support and community. Since they want to focus on Halo Infinite in the future, 343 announced the MCC team will mostly get integrated into the Infinite crew and as such, there will not be enough resources to keep MCC's seasonal model going.
As a result, the eighth season will be the last and Halo Infinite is locked in for December 8, 2021, release. While it's going to be the last, it appears that MCC live support is going out with a bang and the season will be stacked when it comes to the content. At least, that's what the Halo Waypoint post hinted at and it remains to be seen whether reality will be in the ballpark.
It's very much possible 343 just don't want their games cannibalizing each other and are aiming to move the entire player base to Infinite eventually.