Despite some questionable rumors that Apple was delaying Mac OS X 10.5 Leopard until October, Jupiter Research's Michael Gartenberg reports that an Apple representative "confirmed the reports are wrong and Leopard is still scheduled to ship in this spring as they previously announced."
Again, "Spring 2007" gives us a timeframe up to and including June, which is when the Worldwide Developer's Conference takes place.
Meanwhile, there has also been recent speculation that Leopard is not far enough along to ship in April as (Page 2) rumored.