OS X 10.10: Control Centre
OS X Mavericks has a Notification Centre, so perhaps Apple will decide to bring iOS 7's Control Centre to OS X 10.10.
OS X 10.10: iOS 7-esque design
iOS had a complete makeover with iOS 7, adopting transparent elements and ditching skeuomorphism. Mac OS X has yet to take on the new look, but it's quite possible that it will have a redesign that takes cues from the minimalist style of iOS 7 under the leadership of Apple's designer Jony Ive.
OS X 10.10 mockups, concepts and leaked images
While there are no leaked images of OS X 10.10, we have seen a really gorgeous iOS 7-esque concept (below).
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