I think they might be retiring Media Center slowly or something. They have cut it out from Windows 8, and it's a separate purchase altogether (unless you were an early Windows 8 adopter and got it as a free download). I doubt they'll have NO streaming solution whatsoever, but it's hard to figure out what is possible without a console in our hands to find out.
Also, I'm a bit concerned about the profile-switching. How smart is this Kinect, REALLY? If I'm playing a game, and some jackwagon relative comes in and says "show my stuff," is it going to kick me out?