Google has begun the visual PR update. For those who don't know, "visual PR" (also known as "toolbar PR") refers to the "Pagerank" value that can be found on the Google toolbar. It is represented visually by a green bar with a scale of 0 to 10.
Various webmasters began reporting the update earlier this evening. I was able to confirm the update by checking PR values on various Google datacenters (IP addresses). If you would like to quickly check your own pagerank values across a variety of datacenters simply visit the following url: http://www.seochat.com/seo-tools/future-pagerank/
Google PR updates generally occur every three to four months. The last one occured in late April of 05'.