Pretty much this.
It has feature creep now, and they are missing deadlines.
We know that Silicon Dust hardware CAN record protected content right now, as can be seen via WMC + playready.
They are well aware of the CableLabs requirements, and, already have DLNA as shown here
http://www.silicondust.com/dlna/ and it shows : 'Copy protected channels require support for DRM (WMDRM or DTCP-IP)'.
What they don't have is the ability to record that protected stream, which is what everyone is waiting for.
Look at all the PVR type programs out there, you have MythTV (open source,
https://github.com/MythTV), SageTV (open source,
https://github.com/google/sagetv), then there is NPVR, Kodi, MediaPortal, Tvtime, and a few others.
Most of these can use the silicon dust hardware without issue, they can right now record, playback, and some have guide data as well (like NPVR).
What is missing here is the DRM bits that would allow them to record protected content to be a full replacement for WMC.
They need to have a 'playready' type library, then, all those mentioned above could easily fulfill what was lacking before.
Then, SD could have made their own PVR and take however long they want to get it done.