Phil Spencer: Microsoft is working on First Party titles with Japanese studios
Spencer's answer was that, although nothing can be announced yet, Xbox Game Studios is working on several titles in collaboration with Japanese studios. So let's imagine these are titles developed under the wing of the Xbox Game Studios Publishing section, which deals with producing First Party titles made by third-party developers (which many also improperly call "Second Party").
Unfortunately, if these titles have not yet been announced, it means that their release is not too close, and probably Microsoft wants to avoid making the same mistake made with Scalebound, fueling the hype around a very immature game that then did not come out: we will have to wait for these projects to be closer to launch to find out what it is. Let's hope it doesn't take too long!