iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Apple Fixes FaceTime on Older Versions of OS X, iOS 6 Still Not Working
Apple, however, has not yet addressed the problems with FaceTime that are in iOS 6. While it is encouraging that Apple released an update for FaceTime for OS X 10.6, Apple support's recommendations for iOS 6 users has been to upgrade to iOS 7. One user has quoted Apple support as saying that the only fix for iOS 6 is to upgrade to the latest version of iOS 7, with no current plans to release a fix on iOS 6 or iOS 5.
According to Apple's updated FaceTime troubleshooting page, users who are still having trouble with the application are recommended to update to the latest version of iOS or OS X.