The Jackrabbit community is considering moving the components that
rely upon JCR API (and independent of the Jackrabbit implementation)
into a "JCR Commons" project (or projects). See this thread for
details:
http://www.nabble.com/Apache-JCR-Commons-td20795038.html#a20795038
It's pretty interesting, actually.
Also of note is the talk about adding a CMIS implementation that is
also JCR independent:
http://www.nabble.com/jcr-cmis-sandbox-td20789337.html#a20799283