This seems unlikely because most of the Flutter stack is implemented in Dart, except for the low-level graphics library. It would be more of a fork / rewrite.

That is the only way to keep Flutter relevant.

Right now, in what concerns iOS and Android, Qt and Xamarin also compile to native, use mature languages (JS, C++, C#, VB.NET, F#), can also target desktop and have an endless list of libraries to choose from.

Also Chrome team is quite interested in making PWAs succeed on mobile Web, and they have Microsoft on board with them, given how JavaScript has first class support on UWP.

With Dart2 going through LLVM to make ARM binary code for iOS and Android (and Fuchsia), I imagine it would be trivial to emit WebAssembly as well. Writing Dart to make WebAssembly code is far more direct than writing C# and running MSIL on top of a micro .NET runtime (which is what the Blazor project is doing).

Anybody looked at flutter for Haxe?

> will be Flutter bindings implemented for other languages sometime

I hope so