Along with a preview of iOS 8 Apple will preview OSX 10.10 at WWDC later today. OSX 10.10 is rumoured to be called Yosemite or El Cap based on banners on display at the Moscone Centre.
Apple's desktop and mobile platforms have never looked more different. When iOS ditched textures for flat design in iOS 7, OS X took a few of those cues, but it didn't go nearly far enough. System and app icons still look very textured, and the "layering" of windows over backgrounds — which looks great in places like Launchpad — could use more of a presence.
At the same time, the basic UI of Apple-grown apps such as iTunes, iPhoto and Aperture is long overdue for a refresh. Other music services, including Xbox Music and Google Play, have shown how well a strong visual UI can work, while Adobe Lightroom completely outclasses the experience in Apple's photo apps. It's time for some more spice in the iLife.
OSX and iOS both have Airdrop however these service don't work with each other. Apple is rumoured to fix this issue in OSX.
OSX already has some sort of voice assistance but it is not Siri. OSX will most likely integrate Siri throughout the OS.