Registration is now open for the CC http://wiki.creativecommons.org/Global_Summit_2011 September 16-18 in Warsaw.
Versioning the CC license suite will be a (the) major topic of the summit, which will launch a long process of developing version 4.0. All of the topics raised in the years before Wikimedia sites started using BY-SA 3.0 as the default license (e.g., [im]moral rights, copyleft scope, attribution, compatibility) will be explored.
Any Wikimedians are extremely welcome to attend. Whether or not in the fullness of time Wikimedia sites move to the eventual BY-SA 4.0, it will be at least pertinent for Commons. Summit attendee or not, if you're interested in BY-SA 4.0 (and the rest of the CC license suite), I encourage you to subscribe to the low volume, moderated http://lists.ibiblio.org/mailman/listinfo/cc-licenses where further announcements and discussion will occur.
Thanks, Mike