More than a week has passed since many people, e.g. bagginsbill, have asked clarifications on the level of accessibility to the Cycles engine thru the Material Room.

Why this silence? It does take two minutes to write a post "all Cycles nodes will be mapped into the material room". Unless the answer is the understandable letdown of "forget it, you will only get what Firefly exposes today".

I think they're not done with the changes to the material room, from what I read, to give the answer. I would imagine additional nodes specifically for Cycles need to be added to the material room, and possibly some type of script to convert current materials to a format cycles can use. I doubt all shaders can be converted since they are specific to a particular render engine; so things that use actual maps will be easiest to port over.