Matt let the WP-Hackers mailing list know that WordPress 2.0 will be released:
Wednesday or Thursday, depending on the phase of the moon.
Unfortunately that means that many people will be working this week on changing their things over to WordPress 2.0, leaving those that are not ready to upgrade behind. One such person changing over is Michael Heilemann and his K2 package which is not really a just a theme.
Source: Binary Bonsai