The real answer:
Never.
The next move for MS will be a prepackaged Windows "livingroom PC", that you cannot crack open and fiddle with, much like Dell's "cute" mini PCs. MS was never about games. They were always about taking the PC-ness of the livingroom console and making it their own.
Once they establish themselves as a serious livingroom contender (as they have nearly completed doing), they'll hit the PC and console market with the same product, and cement Windows and Office in place, as well as "Games for Windows 7", for the next couple decades, with no fear of Sony/Nintendo outing Windows PCs as the primary browsing, etc. utility of the home.
I wouldn't be at all surprised if said prepackaged livingroom PC had BC for the 360, either.
In a sense, the "next box" will merely be a replacement for your PC. And, like with Vista, MS will try to force everyone to upgrade, by not updating XP, Vista, etc. with the latest software technologies, but providing it on the "NextBox", or spendy licensed, proprietary PC-maker PCs, only. Dell, Gateway, etc... onboard with that -- no homemade PCs? hells yeah for them.
What better way to combat OS piracy, than to effectively disallow people from making PCs capable of running the latest OS? PC checkmate. And who needs a home console, when your home PC has HDMI/Component out, and plays premade console-style titles, as well as runs IExplorer (and no other browser), and MS Word (and no other competing office products)?
