Google latest update was last month, but usually it updates every 3 months. For you to get higher chances of getting crawled, make sure you regulary update your site contents and focus only on the keywords that are relevant to the theme of your site.Bookmark
No one can say that after 3 months Google update the PR, but as previous record say that Google update the PR after 3 months.
I second that!! There are lots of top 5 ranked pages with lower PR than pages with higher PR that rank much lower! Just concentrate on your SEO strategies and efforts, if you focus on raising the PR you loose valuable time.