Apparently Microsoft has something called Windows Server 2012 for Embedded Systems. Would be an interesting base for a television gateway/home server like device. Unlike using RT for a "Q" all the drivers should work on it. Should be possible to use Media Center from 8 Pro on it--if Microsoft permits.
Server Appliance requirements:
1.4GHz x64 processor
Available Disk Space Minimum:
Note: 32GB should be considered an absolute minimum value for successful installation. Computers with more than 16GB of RAM will require more disk space for paging, hibernation, and dump files
Contact a Microsoft Authorized Embedded Distributor for details
10-year product support lifecycle**
However, wouldn't be surprised if this all has to do with the rumored next Xbox. The device could include network tuner support with recordings to be stored on Windows 8 machines and not require 8 Pro. Recording from the Xbox could be copied in the background when network bandwidth is lower (like WHS). Xbox would stream on its own, but you need an Xbox with a HD or SSD and a Windows 8 machine to record TV. Making extenders unnecessary. If the Xbox includes a Blu-ray drive could be interesting.
Of course the primary reason for Ceton to stick with Microsoft is support for DRM. But any other CableLabs authorized DRM scheme would put Ceton in a similar position.