WWDC 2014 to Focus on OS X 10.10
WWDC 2014 is going to mainly focus on OS X 10.10, according to 9to5Mac. They say that there will only be OS X 10.10 so more attention can be focused on OS X than iOS. As many rumors has said, this version of OS X will include more integrations with iOS. Allegedly, Apple has moved some people from the iOS team to work on OS X so it'll be ready in time for June.
Apple first started merging OS X with iOS back with Mountain Lion. It included some things found in iOS, like notifications, iCloud, and more.