Thank you Anne for clarifying my confusion between "activities" and "working groups". It was indeed the W3C announcement that caused my confusion when I misinterpreted the following quote:
The Compound Document Formats Working Group chaired
by Kevin Kelly (IBM) moves to this Activity, and continues to develop a
framework for combined documents
as an indication that the CDF WG would be absorbed into either the Web Applications or Web API Working Groups. Ok, I learned something new today...