Hey,
After a brief discussion on #wikimedia-tech I was recomended to point this out at the mailing list.
We have had requests waiting for this for quite some time. Most notably Chinese projects which have been on hold since December 2006 (bug #8217 [1]) and many others[2] since. The task involves a number of steps for which a documentation was created[3] but never tested as far as I know.
I feel this issue needs a higher priority particularly because the problem becomes more difficult as wikis grow in size with time making the process of a rename more difficult.
[1] https://bugzilla.wikimedia.org/show_bug.cgi?id=8217 [2] https://bugzilla.wikimedia.org/show_bug.cgi?id=19986 [3] https://wikitech.wikimedia.org/view/Rename_a_wiki
-- とある白い猫 (To Aru Shiroi Neko)