The web components under the hood would still need a way to program themselves in response to that data, so a templating language would need to be baked in along with data binding.

Secondary languages are a bad idea, so hopefully this templating language would be something like jsx/ejs.

The proposal really is to bake applications support in to the browser. That seems right to me. The browser is more and more an os, and it should support rich applications out of the box.

React is derivative of windows application development, so there is precedent for something like it to be baked in to an OS.