I was reading the IDPF homepage today, and noticed that they announced in August that they have created a working group to maintain the EPUB standard. It seems they will be working through 2010 and publish updated specifications at some point(s).
I thought folks here might be interested to keep an eye on things, though I'm sure whatever happens will be glacially slow. =P
The press release:
http://www.idpf.org/pressroom/pressr...ntWGLaunch.htm
The work group charter (goals, etc):
http://www.idpf.org/idpf_groups/epubmaint.htm