"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Seeds Fifth Beta of iOS 10.3.3 to Developers
Registered developers can download the fifth iOS 10.3.3 beta from the Apple Developer Center or over-the-air with the proper configuration profile installed.
There were no significant features or notable bug fixes found in the first four iOS 10.3.3 betas, suggesting iOS 10.3.3 is an update that's minor in scale, focusing primarily on security updates and bug fixes.
iOS 10.3.3 will likely be one of the last updates to the iOS 10 operating system as Apple shifts development to iOS 11. The first beta of iOS 11 was released to developers on June 5 following Apple's Worldwide Developers Conference keynote, and two betas have been seeded thus far.
Update: A public beta is also available.