They already did a MR Halo game.Exactly. Those 5 games alone are enough for me (especially since I'll probably only buy 3 at max. SoT, CD3, Ori2). The rest of the games I'll get from 3rd party.
The other Halo related game is probably what I alluded to earlier, a Windows Mixed Reality game (VR). The same goes for Forza as they alluded to new types of things this year as well. Those are probably PC focused experiences.