While Drupal keeps releasing updates to its 6.0 version (originally released in February 2008, last updated, Drupal 6.16, March 10, 2010), it has also just announced that it plans on releasing its newest version, Drupal 7.0, in the next three months, according to an article by PCWorld.
WordPress released its latest version (2.9, Carmen) December of 2009, and Joomla! has not set a date for the release of its newest version, Joomla! 1.6, although that too could happen soon.
Drupal 7.0 is supposed to improve on some of the criticisms earlier versions have faced, such as ease-of-use issues, which have allowed Joomla! and WordPress to grab large chunks of the low to mid-end CMS market.