Apple will not be shipping Mac OS 10.5 (a.k.a. "Leopard") at their Worldwide Developer Conference in June as originally planned but will instead ship in October.
According to a brief statement posted on the company's Hot News Web site, the next major revision of the Mac operating system slipped four months because OS X developers were drafted by the iPhone team to help meet their June deadline.
...iPhone contains the most sophisticated software ever shipped on a mobile device, and finishing it on time has not come without a price — we had to borrow some key software engineering and QA resources from our Mac OS X team, and as a result we will not be able to release Leopard at our Worldwide Developers Conference in early June as planned. While Leopard's features will be complete by then, we cannot deliver the quality release that we and our customers expect from us. We now plan to show our developers a near final version of Leopard at the conference, give them a beta copy to take home so they can do their final testing, and ship Leopard in October. We think it will be well worth the wait. Life often presents tradeoffs, and in this case we're sure we've made the right ones.