Apple today seeded yet another round of betas for its next minor updates, which include iOS 11.4, macOS 10.13.5 High Sierra, watchOS 4.3.1, and tvOS 11.4. The iOS 11.4 beta 5 update comes in at about 2GB - depending on the device that you're using - which means that this is likely to be a release candidate.
New features in iOS 11.4 include the illusive Messages in iCloud and AirPlay 2, both of which were announced when iOS 11 was, and kept getting pushed back into later updates. Apple has said that they would arrive in an update to iOS 11 at some point, and since this will be the last one, we should see them in the final version.
There are still some known issues, which have to do with Foundation, Vision, and Xcode.
macOS 10.13.5 High Sierra has a new 64-bit testing mode, which prevents 32-bit processes from launching. This is because a future update to the OS, likely 10.14, won't support 32-bit apps anymore. Known issues include Foundation, and there are some significant issues with Messages that may cause it to be unresponsive at launch.
watchOS 4.3.1 doesn't really contain any notable new features, and there are no new issues. tvOS 11.4 beta 5 just includes a known issue for Foundation.
Apple's WWDC is only a few weeks away, and at the conference, the firm will show off its next major updates, including iOS 12, macOS 10.14, watchOS 5, and tvOS 12. Developer betas will be released shortly after, so these minor updates should be released to the public at some point between now and then.