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?
Not slowly. Media Center is dead. Media Center was it's own OS edition back in the XP days. It was a legacy app (no new development) since Vista and Windows 7. It's not even a part of Windows 8 (they had a way to install it on Windows 8. I believe as of 8.1 this is not even allowed.)
Media Center is gone. It was nice, but no one bought it (not trying to discount you, I mean not ENOUGH people bought it). I have every expectation that XBox One will eventually have DVR capabilities of its own, but the pushback from providers meant it was a bad idea to try to get it in before launch.
I still use my home server for movies, so I hope XB1's DLNA support is more robust than the 360's.
Vista (and possibly 7) had SKUs with media center (that I believe cost more) so in a sense you did have to buy it. I used to use and love it back in the day, but I wouldn't hold your breath for support showing up. It'd be nice if they'd allow me to hook my HD-DVD player up to the One as well, but I'm not holding my breath.