Apple debuted the first iPhone at WWDC 2007 and has typically used the conference to unveil new hardware products like subsequent versions of the iPhone and now the iPad. This year they didn't and here is I think why.
Apple pulled a rather unceremonious move and pre-announced their announcements, letting the public know they were going to talk about Lion, iOS 5, and iCloud. Some thought it was damage control because no new hardware was scheduled to be announced, while others hoped it was to mislead the public and hit them over the head with a major announcement.
Well the major announcement this year came in the form of iCloud, and iTunes Match. These game changing (if they work as described) services were to Apple deserved of the spotlight. But, that doesn't mean if a new product was ready, they wouldn't have unveiled it. Apple after all is a creature of habit, as are their customers.
The release of the white iPhone 4, the iPad 2, and updated iMacs and laptops makes for a super saturated marketplace for Apple. Introducing a brand new iPhone could canabolize sales of these recently released devices. Also, a lack of heavy competition from competitors, and healthy sales numbers of current Apple devices, has allowed Apple to delay revealing their next phone.
This lack of pressure has allowed Apple the leeway to push out iOS 5 this fall, which I believe will coincide with the release or at least the announcement of a new iPhone. Apple can't wait until next years WWDC to unveil a new phone, and even pushing it to the beginning of next year is testing consumers limits. It makes perfect sense for Apple to at least unveil the new iPhone alongside iOS 5. That way the new device ships with the latest operating system, and comes just in time for the holiday season. I see no other reason for Apple to delay the release of iOS 5, other than to spur even more interest in a new device. Users want the features now, and it appears to be very much in working order.
It's a win-win for Apple. They get to continue to sell iPhone 4's like gangbusters, use the extra time to ramp up production post-earthquake, and capitalize on the holiday buying fever. There are enough new Apple products to keep users distracted in the meantime.
Still, the next few months, waiting for the official release of iOS 5 is going to kill me.