Word on the street (or in this case, the Twitter feed of @TechnicalHalo) is that several MCC devs received the thank you plaque and letter in the image above, which indicates that we may have seen the final update of Halo: The Master Chief Collection.
After an extremely rocky start for MCC, 343 Industries continued to chip away at resolving issue after issue for years, and added a load of new content, making the game extremely popular among fans.