So your Google Toolbar might not reflect the final new PageRank during an update. To check out what PageRank your website might be after the upcoming update, there are several tools that help you to get to know what is the possible Page Rank value of the URLs.
Note: PageRank is no longer as important as it used to be, and is no longer published officially by Google through Google Webmaster Tool. As the result, most of the PageRank tools no longer work.
One of the PageRank checking tools is from
Other PageRank checking tools are from
PageRankTool, Pagerank Check and McDar Datacenter Quick Check (no longer available).