Apple is currently planning to release Mac OS X 10.5 Leopard in June, mostly likely at or around its Worldwide Developers Conference, reliable sources report. As recently as January, Apple had been targeting a ship date of end March but in recent weeks the company moved the date back. The reason for the delay is not publically known but one source noted that "Leopard is shaping up to be a more significant release than anyone expected, with much more to come than any of the developer builds have led on.”
Also scheduled for a June release now are new versions of Apple's iLife and iWork suites, which will pack extensive Leopard-dependent features. Sources say Apple continues to toy with the idea of bundling one or both suites with the new operating system free of charge in an effort to further play up the extra value and features Mac OS X offers over Microsoft's new Windows Vista. In addition, there is a reasonable chance that Apple will drop its yearly naming convention for the software suites entirely, sources report, (possibly replacing 07 with Leopard Edition or a similar naming convention), probably so as not to appear older in consumers' minds in comparison to the competition, such as Office 2008 for Mac.
Source:→ Think SecretApple, Leopard, Mac OS X 10.5, Operating System