User blog comment:Sactage/Technical Update: July 31, 2012/@comment-4674838-20120731224629/@comment--20120801155317

That's hard to determine exactly when. By the end of the month of August, most all active wikis should (I use that word because I can't promise anything, that's just a reasonable and well-informed estimate) be transferred over. As a failsafe, our Engineering team is working on a plan to make sure all wikis that are being used get transferred over first, we'll announce details about that in a later weekly TU when those are firmed up.