Microsoft and 343 Industries are gearing up for the release of Halo Infinite, taking place after the events of Halo 5. For those that aren't aware, this game is part of the Reclaimer saga, which centers around the Foreunners, an ancient advanced alien species. However, Halo Infinite isn't the only new Halo game slated to be released. A new job listing posted by the developer states that a new Halo project is also currently in the works, or at the very least, about to start production.
The listing is for the position of Senior Producer, it mentions in the description that the person who fills the position will be working on “a new project in the Halo universe". Besides that quick note in the description, there's no other details or clues as to what it could be. It is, however, exciting to know that 343 is working on other titles in the franchise. The way its worded gives the impression of a spin-off title, pherhaps Halo Wars 3. It could also be something similar to Halo 3: ODST, where the player saw the viewpoint of ODST troopers rather than 117 himself.
Whatever the game turns out to be, we know it will be quite some time before anything official is announced. As for now, Halo Infinite is slated for release on Xbox One, Xbox Series X, and PC this Holiday, with a glimpse at the gameplay in July. 343 Industries is also working on the gradual rollout of Halo: The Master Chief Collection on PC, with Halo 3 next in line to come out.