Back in June I reported on how Google's Checksum algorithm was backwards engineered. Since then, dozens of PageRank tools became available. There has been a few backlink updates at Google since the checksum was available, but PageRank has not been changed in about three months. In fact, Google has been slowly taking away hints for the SEOs to learn if they are improving in link popularity.
There is a post over at SEO Chat named New Google checksum algorithm where PRWeaver posts the fact that Google is releasing a new toolbar version. When you download the new toolbar, and then find the checksum figure, you will notice that it doesn't match the old toolbar checksum figure, nor does it match the checksum algorithm that was available for free.
Does this mean we can expect to see future PR updates? Sounds likely to me.
Does this mean that all the tools that have the PR checking algorithm will be useless? Sounds likely to me.