Comment by pjmlp

Xamarin.Forms is currently available for iOS, Android, UWP.

At .NET Conf 2017 they announced support for macOS, Linux and WPF. And demoed macOS and Linux current status.

While previously at BUILD 2017 they announced XAML Standard for interoperability between WPF, UWP and Xamarin.Forms.

Which kind of implies it is the way forward.