Apple seeded the third developer beta of iOS 10.3.3 Tuesday. It’s seen as a maintenance release. Developers can download the beta through their device or iTunes for iOS devices set up with a developer profile.
Aside from wallpaper images for iPad Pro 12.9-inch, there have been no new features announced as part of this developer cycle. Any remaining iOS 10.3.x releases are likely to be security-related in the ramp-up to a Fall release for iOS 11.