stolen from reddit:
http://imgur.com/3SZpIo0
Actual Xbox 360 Halo 4 was running on a phone, tablet, and Windows 8 PC.
Using Azure cloud they were able to already get lag down to 45ms in current testing, will be reduced.
Demo was even said to be running on iOS and Android.
That's all I currently know, I'll update if I get more info.
http://imgur.com/3SZpIo0