iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Apple's Newest Snow Leopard (10A314) Shows Steady Improvements
Apple, however, has not yet deployed the "Marble" user interface changes that have been rumored for Snow Leopard.
An exact release date for Snow Leopard has not been established , though recent rumors have suggested it could be as late as September. Apple will likely make further announcements and demos of Snow Leopard at the Worldwide Developers Conference in June.