It's not sure, but generally after 3 months google updates PR. These days i have seen that google is doing updation once in a week.
The last update on my sites was 2-3 weeks ago, and as everyone else has said it is impossible to predict, but if I had to guess I would say toward the end of August
Interestingly our subpages are give immediate pr or within 4 weeks of the launch of the page these two for example http://www.spanishhotproperties.com/spanish_rentals.php http://www.spanishhotproperties.com/blog/ However our home page still only has a pr3 which i find very strange considering our ranking and content
Don't worry about PR.. worrying about how much traffic your site is generating! That will tell you whether or not what you're doing is right!
Google used to update PR every 3 months ish. However I now feel that they update PR when the feel. So sometimes within weeks of each other. Also I feel that they do many small PR updates, whereas they never used to do this. Josh
The estimate range of PR updates usually around 2 - 6 months. The latest update was end of May. So, the next one could be somewhere between July - Nov.
They typically occur once every quarter (every three months). Based on the PR increases on my own sites, it seems like the last update happened a few weeks ago.
according to me, the latest update that took place was a minor 1...major update will be in July 1st week only (as per the 3 months strategy) my 2 cents