The Structured Documents work group at HL7 is working to create an update for CDA.  This new update will enable wider use of the HL7 RIM structural vocabularies, while at the same time preserving backwards compatibility with CDA R2.  If you have an interest in working on this new version of CDA, You might want to consider joining us on our bi-weekly conference call.  Here is a link to the CDA R 2.1 team call.