Dart is kind of speculative -- but it has the backing to be a big thing in a few years. And since it's the "anti-javascript" I think it adds more to a developers versatility than learning 5 javascript frameworks.
Our dev teams that have adopted it like it, and it's been very successful for them.
I wouldn't call it "anti-JavaScript", but "sane JavaScript".
Dart's very similar to JavaScript in a lot of ways, especially most of the syntax. The main difference is that programs have a static shape, which makes tooling and reading a codebase much, much easier.
Dart's always had to compile to JavaScript - the VM was probably never going into other browsers even if it went into Chrome. All of the developer productivity benefits are still there.
Our dev teams that have adopted it like it, and it's been very successful for them.