Not quite yet, but we're working on it. There are some significant features that KaTeX doesn't yet support, but we're working to add them in the near future.
In the meantime, you could use our TeX React component to use KaTeX when possible, and fall back to MathJax only when necessary: http://khan.github.io/react-components/#tex
In the meantime, you could use our TeX React component to use KaTeX when possible, and fall back to MathJax only when necessary: http://khan.github.io/react-components/#tex