According to Reuters the changes will be available as beta releases late Monday or Tuesday and "will generally be available" in the next few weeks.
The AP article has info on what you'll see:
+ "The most visible changes include the addition of a 'music' button across the top of the home page and the removal of a button that directed traffic to the company's help wanted site, HotJobs."
+ "Yahoo's redesign also includes a new search tab for the site's Web directory and a regularly updated feature that will report on which topics are generating the most search requests."
I just noticed that a beta version of "All New My Yahoo" is online. All of the new features are listed here. Lot's of attention to RSS/ATOM capabilities (now out of beta) along with a new searchable directory containing more than 150,000 content sources (including RSS feeds) to add you your My Yahoo page.
Want to discuss? Please visit our forum thread: NEW: MyYahoo! Beta Upgrade.