As announced on Apple’s developer news site, Apple has just released Xcode 9.3 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.
For users who are planning to update to Xcode 9.3, note that this new version requires macOS High Sierra 10.13.
Update April 3: The Xamarin 15.6.5 release has now been published with SDK bindings and IDE compatibility for the Xcode 9.3 release.
Xcode 9.3 Support Preview Release History
Preview 2 – March 15, 2018
Preview 1 – February 15, 2018