Apple has released sixth beta iOS 10.3.3 and macOS Sierra 10.12.6. Updates are available to users who participate in software beta testing programs, but not to those who participate in tests iOS 11 and macOS 10.13.
The sixth beta of macOS 10.12.6 is available in Mac Updates App Store. This beta release is not related to the current testing of macOS High Sierra 10.13.
The sixth beta iOS 10.3.3 is available in Settings – General – Software update. This beta is also unrelated to beta tests iOS 11.
No major changes are expected in macOS 10.12.6 or iOS 10.3.3, although iOS 10.3.3 includes several water-themed wallpapers. This means that the next updates will be aimed at fixing bugs and improving the security of system software.
Usually Apple releases several beta versions of the system software before the final release. Based on the releases, you can understand the approximate timing, and this may mean that we will see the final versions iOS 10.3.3 and macOS 10.12.6 in the next few weeks, when the system update will be offered to all users.