I was doing some updates to the website and wondered when the next Page Rank update would be and so started doing a quick search for this information. Came across the following site which lists down the trend of the Google Page Rank update. Pretty interesting results.
As of May 12th, there has not been a Toolbar PR export for 12 day(s). The longest time between toolbar PR exports recorded in the below Page Rank Export List was 122 days (Oct 19/2005 to Feb 18/2006).
Source: Page Rank Update or Export List History – PageRank – PR
Also another useful tool would be a Page Rank predictor below:
Google PageRank Prediction
This predictor tool does what it says, it predicts your future Google PageRank.