Protobuf is static enough. And the claim that everything will be broken or abandoned in 6 months is rather chicken-and-egg; at the moment Dart is a young, relatively obscure language, it doesn't have a mature, reliable library ecosystem. But the only way it's going to get there is if people start using it, using its libraries, writing their own libraries, and figuring out what works and what doesn't.

> Doesn't it seem strange that a Google-designed language for the future of the web (that's supposed to make development faster and easier) doesn't handle this (basic) requirement easily?

I don't think it's fair to call this a basic requirement. Scala is a 10-year-old language and the state of JSON serialization is still a mess (it's taken the recent macro system to put us anywhere close to sorting it out). Converting between typed and untyped at the boundaries like this is a hard problem, not entirely solved in any language (Java has basically given up and just used reflection and annotations, which is an answer, but not a very pleasant one). I think Dart is entirely right to take it slowly and make it a matter for third-party libraries rather than a core language feature.