Nobody knows it. Ask it on google forum: http://www.google.com/support/forum/p/Webmasters/label?lid=41234c84d9491af8&hl=en
I am seeing some tweets that pagerank update has started 2 hrs ago,is it spam or true guys?? I am looking for my site site to move to at least PR 3/4. Hope will move >>> update here if you find any information..