DOCBOOK: section.class parameter entity

What release is %section.class; scheduled for?

http://lists.oasis-open.org/archives/docbook-tc/200108/msg00009.html

It's not in DocBook XML V5.0a1.

Maybe I could just have a peak at it? I'd like to make a custumization of 
section, and I might as well aim at something that'll be included in a 
future release of DocBook.

Kind regards

Peter Ring