Apple has just released an update to the OS X Yosemite public beta. The release makes this the fourth beta for the Yosemite public beta preview program, and the update should be available through the Mac App Store for download.
OS X Yosemite is due for a consumer launch this fall. Developers participating in a separate beta program are now being seeded with a gold master of OS X Yosemite, suggesting that Yosemite may soon be launching to all consumers.
At this point, it seems that the roll out is still gradual and the update may not be available to everyone just yet. Have you received the Yosemite public beta 4 update?
Source: Apple developer