Please take note of this Report as well: WordPress 3.0 released (June 17).
The last wordpress 3.0 planned release date for May 1st has been postponed again according to the official development schedule. Wording changed from release to first RC. The next written release date is now May 15th, but that date has already been flagged with a question mark. It is likely to show that this date is highly vague, which leads to the assumption that practically there is no concrete release date planned for WordPress 3.0 right now.
Please take note of this Report as well: WordPress 3.0 to be shipped early next Week (June 12).
The project currently faces a lot of issues related to the merge of two code-bases that had the same root but were developed in parallel over the last years: WordPress and its fork WordPress MU. MU didn’t get much love and many security fixes needed to be backported from WordPress to MU. In the end MU was way behind. In May 2009 Matt Mullenweg announced that he wanted to see WordPress merging with the years-ago-fork. He is founder of Automattic Inc., the company that publishes WordPress.com which uses MU.
That merge started in the beginning of January by committing MU code into WordPress. This on its own is one of the largest changes for a new release in the history of the open source project.
The launch of the third point release was originally planned for April 13 2010, but has been postponed the first time on feature freeze 1st of March.