Pagerank is an algorithm used by google search to rank websites in search results. Pagerank toolbar is available as a browser addon to check the ranking score of the websites. It was updated 3 - 4 times a year and report says that the last update of pagerank was on february 2013. There was one more update in December, but Googlers said that it came out by accident during some database maintenance.
Google's John Mueller said in a Video of Google+ hangout that Google will probably not be updating Google Toolbar pagerank in the future.