I would focus on making React stable, fast and lightweight but improve on tooling and ecosystem around it.
* I would like blessed way of extracting React components, so they can be reused between projects (like right click in IDE and share) - something like https://bitsrc.io/
* react addon for chrome could be much nicer (I have to dig through so many unnamed HoC sometimes).
* you could favor more beginner friendly state solution - something like https://github.com/solkimicreb/react-easy-state
* you could embrace typescript for easier usage experience
There could be some React plugin(kinda like http://demo.rekit.org/) for editors that would allow for:
* adding mock props to component and preview it on hover, click for example (kinda like styleguidist but with less setup overhead) * abuse above to provide out of the box image snapshot testing * simpler ability to add tests (like right click on component and "add assertion", "go to test") * some structured way of making components * swap between style, tests, data sources and logic * run tests only for this component * etc - basically more streamlined creation experience
Also please focus on debugging when introducing async rendering. (so there won't be errors out of nowhere in stack trace)