I still don't see any big advantages over Xamarin Native, Qt or plain C++ with native views, when going through this route. All of the with the bonus that C#, JavaScript and C++ actually have lots of market demand, Dart remains a possible CoffeScript.
Speaking strictly to the Xamarin here... as someone who has worked professionally w/ Xamarin, Xamarin.Forms, and Flutter: Flutter knocks it out of the park. My experience with Xamarin was so buggy as to be nearly unusable (on Stable no less!). The documentation, _especially in Xamarin.Forms_, was sooo lacking! I wanted so hard for it to be "the next great thing", but there were just too many gotchas and pain points.…
For me having to deal with Dart, a programming language without any other purpose than Flutter, it rules out any advantage over Xamarin.
With Xamarin I have C# and the whole .NET ecosystem available.