As announced on Apple’s developer news site, Apple has just released Xcode 9.4 final.
The Xamarin team is proceeding as usual to test for compatibility and publish updated versions of Xamarin.iOS and the Visual Studio Tools for Xamarin to align with the new version of Xcode. Keep an eye on this blog for status updates.
Update May 31: The Xamarin 15.7.3 update has now been published with SDK bindings and IDE compatibility for the Xcode 9.4 release.
Xamarin.iOS Xcode 9.4 Support Preview Release History
Preview 2 – May 10, 2018
Preview 1 – April 16, 2018