There's still no official word from Microsoft on what it's Xbox 360 successor plans are, but multiple sources "familiar with Redmond's plans" tell Polygon that the company's first steps into the eighth hardware generation will happen in 2013. It sounds like Microsoft will be offering options suited to both a casual gaming audience and a serious gaming audience, with the new device taking the form of a set-top box.
The box will be powered by "core components of Windows 8" and will "support casual gaming titles rather than full Xbox games typically found on a dedicated console." Presumably the other half of this two-pronged hardware attack is better equipped to deliver the sort of entertainment experiences that Halo fans would be after. The word from Polygon's sources is that the set-top box work is also meant to gauge how scalable the next-gen Xbox framework is, with the goal being to bring the Xbox experience to an assortment of devices.
Interestingly, Microsoft didn't respond to the expected request for comment with its standard "we don't comment on rumors or speculation" line. Instead, the company issued a statement with the strong suggestion that change is in the air, without actually confirming anything. See here:
Xbox 360 has found new ways to extend the console lifecycle by introducing controller-free experiences with Kinect and re-inventing the console with a new dashboard and new entertainment content partnerships. We are always thinking about what is next for our platform and how to continue to defy the lifecycle convention.
It's notable that the AAA game release schedule for 2013 doesn't extend much further than the spring. The fact that Microsoft has a March release set for its next Gears of War game is also a big red flag. Fall 2013 is looking more and more like the release timetable for the next phase of Microsoft's Xbox evolution, whatever that might mean.