iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Apple Shares WWDC OS X Yosemite Video Highlighting Design Changes
Covering the changes to the dock and icons along with showing off Yosemite's translucency, the video also highlights AirDrop, Finder, Messages, and Notification Center, giving an overall view of the revamped OS.
We reconsidered every element of the Mac interface, large and small. The result is something that feels fresh, but still inherently familiar. Completely new, yet completely Mac.First introduced last week, Yosemite includes significant design changes that focus on translucency and a flatter, more modern look, along with a push towards deeper integration with iOS 8. Yosemite introduces several new features that work with iOS 8, including Handoff, Instant Hotspot, and the ability to make and receive phone calls and SMS messages.
Multiple apps and features have also been updated, including Spotlight, Mail, Notification Center, and Safari, and there's a new focus on iCloud with iCloud Drive. More information on Yosemite's major changes can be found in our OS X Yosemite Roundup, while details on smaller tweaks can be found in the "OS X Yosemite: All The Little Things" forum thread, created and maintained by MacRumors forum users.