I've posted some notes from the working group call that was held yesterday - they are available at:
http://gnuradio.org/redmine/projects/gnuradio/wiki/Call20150211
Additionally, the main item that came out of the call was that we should clearly document what use cases require changes to mainline GNURadio. The primary interest here is ensuring that
1.) GNURadio remains hardware-agnostic, and only includes the interfaces required by OOT modules to support specific platforms/co-processors/hardware, and
2.) making sure we don't make API changes now which don't support future use cases that result in API-breakage in the near-future.
I encourage everyone interested in this topic to take a look and edit/comment/etc. I do plan on adding some more content to this in the coming week, but I want to gather as much input as I can so I'm putting this out now. I'll note that most of what is on there right now is just a collection of the discussion notes from the previous WG sessions (i.e. GRCon'13 and GRCon'14), but the goal is to have a coherent picture of what exactly is desired, and what changes need to happen to GNURadio.