Fortaleza glasses work by providing an ‘augmented reality’ 3D image anywhere the user looks, allowing the ‘720 to jump offscreen. In conjunction with mapping via the Kinect V2, this could allow for a game that maps fully with its environment, and even interacts with it. Left for Dead 3 could make for a pretty amazing and personal game.
The actual methodology is somewhat like the Google ‘Project Glass’ concept and while not fully fleshed out in the document, it’s apparent that Microsoft hopes to leverage on any success in Fortaleza to make the 4G network glasses a consumer item in the real world, directly competing with Project Glass.
The final string the doc outlines for the Xbox 720’s bow is that Microsoft look at it as an end-game in the console world. As computing power accelerates in the future, the 720 is planned to become a streaming device, delivering essentially unbounded graphics and capabilities over the web, all plumped down via the power of the console itself and the connectivity it offers.

While we've cut to the meat of what it contains, the document itself has a bit more detail - however most of us will have to wait until it becomes public - use of the widely available torrents of this document would be unethical.
Currently Microsoft have given no real comment about their next-gen console. However given how forward looking this 2010 document seems to be, Atomic is more than a little interested to see about the actual hardware and capabilities of Microsoft's next-gen console as it emerges.