"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Seeds Third OS X 10.11 El Capitan Beta to Developers
The update is available through the software update mechanism in the Mac App Store and through the Apple Developer Center.
OS X El Capitan largely builds on the features introduced with OS X Yosemite, focusing on improving performance and user experience. Behind-the-scenes improvements in El Capitan have made a number of apps and processes on the Mac much faster, and the introduction of Metal makes system-level graphics rendering 40 percent more efficient.
Along with a new systemwide font, El Capitan includes a revamped Mission Control feature, a new Split View feature for using two full-screen apps at once, deeper functionality for Spotlight, and several new features for Safari, including Pinned Sites for housing frequently-visited websites and a universal mute button that quiets all tabs.
OS X 10.11 El Capitan is currently only available to registered developers, but Apple plans to offer a public beta of the software in July. Following testing, El Capitan will see a final release in the fall of 2015.
What's new in OS X El Capitan beta 3:
Two-Factor Authentication - iOS 9 and OS X 10.11 El Capitan include an entirely revamped two-factor authentication system.
Photos app - As in iOS 9 beta 3, there are new albums for selfies and screenshots in the Photos app in El Capitan beta 3.