Apple today seeded the fourth Developer Beta builds of iOS 10.3, macOS 10.12.4 Sierra, and watchOS 3.2. Apple Developer has only been updated to reflect the iOS and macOS builds, so it's still possible that a tvOS beta may be on the way as well. The news comes just one week after beta 3 was released.
iOS 10.3 will contain a few new minor features, such as support for AirPods in Find My iPhone and weather forecasts in Maps. SiriKit has some improvements as well, such as the ability to make payments and order an Uber, and there are improvements to HomeKit and CarPlay.
The release notes for iOS 10.3 beta 4 show a number of fixes for this build, but they're all the same as they were last week. They include fixes for iCloud Analytics, iCloud Backup, LAN Asset Cache, Lightning video adapters, managed and shared devices, and Xcode Simulator.
macOS 10.12.4 Sierra will also contain some new features, most notably Night Shift, which reduces the blue light emitted from the screen, and should allow you to get to sleep easier. Siri also gets support for checking Cricket scores, schedules, and player rosters from the Indian Premier League and International Cricket Council, and there's dictation support for Shanghainese.
There's nothing new in the macOS release notes, which isn't surprising. The watchOS 3.2 release notes don't exist yet, as Apple Developer hasn't been updated to reflect today's release yet, over an hour later. The update itself will include a new Theater Mode and support for SiriKit.
Update: iOS 10.3 and macOS 10.12.4 Sierra Public Beta 4 are now available.