In 2007, Steve Jobs presented the iPhone at MacWorld after rumors swirled about an Apple produced smartphone for almost two years. After the phone was showed off to the world, Apple waited until late June to actually release the device. This gave the iPhone a chance to receive press coverage, feeding the hype machine, until the iPhone became larger than life. Apple used the time between introducing the device and its actual launch, to make sure that everyone not only wanted an iPhone, but that everyone felt that they needed the iPhone. It also gave Apple the time to hone its marketing strategy, which obviously worked to perferction.
With Apple expected to introduce iOS 8 at WWDC, why wouldn't Apple want to show the synergy between the latest build of its mobile OS and its latest mobile device. iOS 8 is expected to offer an app called Healthbook which is rumored to be a repository for all of the information and health data that the iWatch sensors come up with.
WWDC will be held from June 2 through June 6th this year, and if Apple returns to its tried and true new product introduction strategy, by June 7th a large percentage of the world's population will want an iWatch.