From Apple's Hot News web page:
iPhone has already passed several of its required certification tests and is on schedule to ship in late June as planned. We can’t wait until customers get their hands (and fingers) on it and experience what a revolutionary and magical product it is. However, 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. [Apr 12, 2007]
This is interesting. Apple, like many companies often slip their release dates. Historically, however, Apple has only slipped a little on ship dates, but this slip, from Spring 2007 to October 2007, is the largest slip I remember. It's very uncharacteristic of the rhythm of shipping Apple has had over the last 5 years.
Leopard is certainly Apple's most ambitious OS release yet, so it stands to reason that they could have bit off more than they could handle. I'm sure this was further compounded by the additional resources needed for both the Apple TV and the iPhone. I also wonder what the "secret features" are that Jobs referred to in his last keynote. Some have suggested that this slip was to add unplanned functionality, but I don't get that sense. I tend to believe that this is just what it's stated to be, a resource issue.
There are 3 variables you can change when managing a project: scope (how big it is), resources (how much money and people you can allocate) and time (how long the project will take). It looks like Apple reduced their allocated resources for Leopard, and without a corresponding reduction in scope, they were forced to increase the time the project would take. I'm sure this is super painful for them, it always is, but not long from now, they'll ship and this will all be a distant memory. Personally, I'm glad I don't have to put up with all the rumor sites constantly suggesting that Leopard is just about to RTM. ;-)
Update: Best quote from our chit chat around the office here: "Woah. October? :( Stupid iPhone. I want my Time Machine."