As per the licensing update decision by the community and the Board, I've updated the site terms on the English Wikipedia (and the WMF website) today, and posted a reference copy of the site-wide terms of use to:
http://wikimediafoundation.org/wiki/Terms_of_Use
The Wikimedia Commons licensing task force has gone ahead and updated the relevant GFDL templates on Commons to indicate that eligible media files may also be available under CC-BY-SA.
The English Wikipedia roll-out serves as a reference implementation and may lead to some final tweaks in the terms and language. In the coming days, we'll begin the translation and roll-out in other eligible projects and languages. Communities will be able to customize the messages and terms within limits, as described here:
http://meta.wikimedia.org/wiki/Licensing_update/Implementation
Our site-wide roll-out will likely override any project-local bottom-up implementation between now and then.