We're going to be upgrading the software on the live site to the current
development version, over the next 24 hours or so. However, we won't be
releasing a tarball just yet. Before we do that, we want to obtain
translations for the new interface text, and also to fix a few
user-friendliness issues with the installer. We'll probably upgrade the
smaller wikis first, and do the English Wikipedia fairly late in the peace.
There might be short periods of downtime during this process.
A list of new features is at
http://meta.wikipedia.org/wiki/MediaWiki_roadmap
-- Tim Starling