As for simple HTTP client, I don't think you guys need to worry. There are plenty of such small tools to choose from independent of react. Plus, most recent browsers have built-in http client support (fetch).
So, in such react-independent libraries, I think, you guys should assess the future of that specific library you are using.
However, I think routing and state management are, for the most part, react specific (I know some can be used outside of react's scope). And I think activity in those areas will affect a software developed using react as a whole.
And for react-router, yes, it caught me off guard as well. And lack of clear documentation made it hard for me to work on it. But a year ago (Mar 2016) the react-router guys said this.