It looks like Microsoft is not going to stop at two nextgen consoles and purchases of large studios / publishers to win the trust of users in the next generation. Cygnifick on the Microsoft Flight Simulator forum reported that the flight simulator files contain traces of VR support for Xbox Series consoles.
The line of code is listed as Scarlett_VR. Recall that Scarlett is the name of the Xbox Series X and Series S consoles family.
Perhaps Microsoft is preparing to introduce a VR headset in the style of PS VR, or it’s just traces of old code. In 2017, there was information that the company was considering the possibility of implementing VR support for the Xbox One X, but the idea did not move anywhere.
Microsoft Flight Simulator is currently undergoing closed VR mode testing.