Umm, I'd be surprised if that was high up on the list of features, as Kinect is hardly that popular on Xbox. Microsoft is no longer manufacturing them, and AFAIK it's officially dead from a Microsoft perspective.
Agree @sudharshan that Kinect was a lot of fun.
Remember that day where I was at a friend and we played a karate-game together on XboX Kinect, which was basically a lot of exercise, because we had to kick/box on our own, but also a lot of fun.
Regarding sports/activity not a bad idea for Stadia, if motion sense could be a thing. Would recommend to leave feedback for this in the Stadia app or on stadia.google.com. From my perspective it would be a nice thing to have.