tedster - 10:56 pm on Jul 5, 2010 (gmt 0) [edited by: tedster at 3:39 am (utc) on Jul 6, 2010]
Google doesn't give out a schedule for PR updates, and in fact Matt Cutts once posted that Google considers a PR update to be a "non-event".
The important information is that it doesn't matter for your traffic - because toolbar PR just an update to the publicly visible, reported amount. Your actual PR is updated all the time.
[edited by: tedster at 3:39 am (utc) on Jul 6, 2010]