This is one of the questions we are all asking ourselves right now, just hours after Apple introduced the new operating systems. In reality, Apple never usually gives an exact date of the launch of its final software until it has it quite polished and worked together with the developers that They already have the first beta version installed on their Macs since yesterday.
If we follow the dates in the last WWDC of 2013 we will see that between the presentation date of OS X Mavericks which was June 10, until the final launch of the operating system for all users about 4 months passed (October 22, 2013) taking advantage of the presentation of the new iPad and this 7 months ago.
This time the new OS X 10.10 Yosemite operating system we hope will have a beta period similar to OS X Mavericks, so we do not expect Apple to change its release schedule and it will finally end Introducing the final version of this OS X 10.10 Yosemite in October as they already warned in the same keynote, autumn.
It is logical that Apple does not confirm an exact date for the release of the final version since there can always be some unexpected problems or failures in the new operating system, I even remember that in the current version of OS X Mavericks Apple released two versions of the Golden Master (GM) which is the version prior to the official release correcting an error that previously escaped them.
How to say: dress me slowly I'm in a hurry, and the guys from Cupertino do not usually run to officially launch the new versions of OS X and less if it is not prepared for all users to enjoy it without failures in the applications that we have on the Mac.