The Xbox Series X was going to be the first Xbox console in four generations to launch alongside a new Halo game. That's substantial because Halo is Xbox's flagship franchise. Hand-in-hand, they can do a lot to help each other.
That's no longer the case. Developer 343 Industries has made the decision to delay Halo Infinite into 2021. No new release window was given apart from it coming next year.
In its message, 343 attributed the delay to COVID-19 workflow issues as the whole studio is working remotely. 343 head Chris Lee goes so far as to say the developer is actively avoiding crunch, stating "It is not sustainable for the well-being of our team or the overall success of the game to ship [Halo Infinite] this holiday."