Previewed at WWDC, launching in the fall.
Apple Seeds Sixth Beta of iOS 11.4 to Developers [Update: Public Beta Available]
Registered developers can download the new iOS 11.4 beta from Apple's Developer Center or over-the-air once the proper configuration profile has been installed from the Developer Center.
The iOS 11.4 update introduces a new ClassKit framework for educational institutions, which supports new features announced at Apple's March 27 education-focused event.
For regular users, the iOS 11.4 update adds features that were originally present in the iOS 11.3 beta but removed ahead of release.
It includes support for Messages on iCloud, designed to store your iMessages in iCloud rather than on each individual device, allowing for improved syncing capabilities. Currently, incoming iMessages are sent to all devices where you're signed in to your Apple ID, but there is no true cross-device syncing.
Messages on iCloud will allow you to download all of your iMessages on new devices, and a message deleted on one device will remove it on all devices. Older messages and attachments are also stored in iCloud rather than on-device, saving valuable storage space.
The iOS 11.4 update also includes AirPlay 2 features, with the Apple TV once again available in the Home app. With AirPlay 2, the same audio content can be played in multiple rooms on devices that support AirPlay 2. AirPlay 2 includes a feature that lets you ask Siri on one device to play content on another AirPlay 2-enabled device. So, for example, you can ask Siri on iPhone to play content on your Apple TV in another room if you're running the iOS 11.4 and tvOS 11.4 betas.
There were initially signs of support for HomePod stereo sound in the first iOS 11.4 beta, a long-promised feature, but stereo sound didn't work properly and the mention was removed in the second beta. It's not clear if it will return for the update's release.
For the iPhone 8 and iPhone 8 Plus, there's a new (PRODUCT)RED wallpaper available, which is not available on iPhone X. During beta testing, Apple implemented a USB Restricted Mode that introduces a week-long expiration date on access to the Lightning port on iOS devices for data purposes if your iPhone hasn't been unlocked, which has implications for law enforcement tools like the GrayKey box. Mentions of the feature were removed from Apple's release notes, so it's not clear if it will be included in iOS 11.4.
With six betas having been released, we are nearing the end of the beta testing period. iOS 11.4 is likely to see a public launch in the next few weeks.
Update: Apple has also seeded the sixth beta of iOS 11.4 to its public beta testing group. For developers, the update is also now available over-the-air.