Part of the irony out of all of this is that many people assumed that the iPhone would make its official debut at Worldwide Developers Conference (WWDC) in the early part of June. Well, it didn't quite work out and Apple had to divert some of its resources to even achieve the late June launch date. They pulled key engineering and QA folks away from developing Mac OS X Leopard so that they could work on the iPhone instead.
As a result, Leopard will be shown in a "near final version" at WWDC, but will not ship until October. The press release goes on to say that "life often presents tradeoffs, and in this case we're sure we've made the right ones."
From:http://www.mobilemag.com/content/100/340/C12349/