Previewed at WWDC, launching in the fall.
Apple Seeds OS X Yosemite 10.10.2 Build 14C94b to Developers
The new beta, build 14C94b, is available through the Software Update mechanism in the Mac App Store and through the Mac Dev Center.
Apple continues to ask developers to focus their testing on Wi-Fi, Mail, and VoiceOver. Wi-Fi in particular has been an issue for some OS X Yosemite users since the operating system's October launch, and OS X 10.10.1 released in November failed to resolve all of those problems.