Recently, it was reported that the Xbox Series X wouldn’t be doing that, and that its UI would instead be rendered in 1080p.
It’s possible, then, that the Xbox Series X’s UI when the console releases will end up being 4K after all.
Recently, GamesBeat’s Jeff Grubb took to Twitter to mention that the embargo sent to him by Microsoft alongside an Xbox Series X for pre-release impressions and previews specifically mentions that the UI and certain elements aren’t final and will be updated before launch.
Microsoft recently detailed the full list of launch titles the Xbox Series X/S will be releasing it.