Google's John Mueller said in a video Google+ hangout yesterday that Google will probably not be updating Google Toolbar pagerank in the future. He said this at 20 minutes and 30 seconds into the video:
We will probably not going to be updating it [PageRank] going forward, at least in the Toolbar PageRank.
In December, when Google updated Toolbar PageRank, it turned out to be not really intentional and I doubt that Google will be updating it going forward.
Goodbye Toolbar PageRank!
Forum discussion at Google+.