Preview at WWDC likely in June, followed by September launch.
Apple Seeds Second Beta of iOS 11.2.5 to Developers
Registered developers can download the iOS 11.2.5 beta from Apple's Developer Center or over-the-air once the proper configuration profile has been installed from the Developer Center.
It's not clear what new features, if any, will be included in the iOS 11.2.5 beta. We didn't discover any noticeable outward-facing changes in the first iOS 11.2.5 beta, so it's possible this update focuses mainly on bug fixes and security improvements.
If that's the case, we may not know the extent of what's in the update until it sees a public release. Apple is supposed to be releasing an iCloud Messages feature that was pulled from the iOS 11 release, but there has been no indication of when we can expect iCloud Messages to be reintroduced.
Should new features be found in the second iOS 11.2.5 beta, we'll update this post. Apple has also released new beta firmware for the HomePod, which will be available to employees currently testing the device.