Flutter is closer, but it is too focused on being a framework. I'm thinking of a platform agnostic protocol with implementations in whatever language you like. Flutter is too many of things at once. If they basically ripped out each native platform's implementation and made it target the protocol I've described, then made their OOP framework target that protocol, then had the two interface using the protocol, that's what I'd like to see. That way you could write React Native on top of that new "Flutter Native Core".