Sometimes looking over the history of Google pagerank and backlink updates can provide insight into what to expect in the future. Here are a few sites that show information about google updates:
Seo Company Google Update Page - this is one of the most popular sources, yet at the tie of this writing, they don't seem to be noticing there have been changes, as noted on the Directory Trials Website.
SEO Logs has a nice graph showing pagerank and backlink updates.
Presentation Rentals seems to track updates as reported on Digital Point, but seems to have missed the last one at the time of this writing.
One of the very first places that displayed the update history was Webmaster World, and you can see what used to be an excellent record.