Hehe, there is no set time or date when google will do any updates. There are billions of pages of the interwebz and google hasn't got time on its side. Unfortunately the only answer is 'when they get round to it'. Work on your SEO and you'll be crawled more often than what you currently are, that's the only best solution to quicker updates of your PR.
google just updated toolbar PR little over 2 weeks ago. another update will not gonna be anytime soon