If I reckon correctly, Mr. Stevie J. said they were going to release the next version of the Mac OS (10.5, or "Leopard") before Windows Vista came out, which reportedly will be happening before Thanksgiving (yeah, right).
So could we expect an announcement about it at this event on the 28th? Maybe a preview April 1st for their 30 year anniversary? Or will it be later in the summer, closer to the relase of Vista?
It's probably too soon for another full-fledged relase, although Apple gave a preview of Tiger in June '04 when it wasn't released until April 2005, ten months earlier. That wouldn't rule out a preview of Leopard now, eight to ten months ahead of time.