Yesterday at WWDC 2014, Apple announced that their next upgrade for OS X will be 10.10 Yosemite and there will be a public beta for up to 1 million Mac users this summer!
OS X Yosemite will have an iOS 7 look and feel and it now has a translucent background and is available to Apple developers today.
See the preview here (http://www.apple.com/osx/preview/):
(http://i58.tinypic.com/cl451.jpg)