I’ve seen many advanced React users make a claim against the preprocessor that state that styled components are the next big thing for styling your sheets.
Now I love learning react as of now and the idea of taking everything into one place for convenience, it’s just we know that there’s still a possibility that there could be a new frame work to fix what React doesn’t have now or more importantly build a new way of thinking when it comes to styling. There could be other future JS frameworks in the works that would pick up this new idea, which is happening with React’s Styled Components via Vue. I’m honestly hoping that the idea with styled components stick around too, but we never know what’s in store.
Having a preprocessor specifically for CSS is a bit more universal. I would rather have the Sass community simply continue improving their frameworks like Vanilla framework or Hocus-Pocus. Then, have React allow developers to use it as a platform for CSS frameworks, but we never know what new technologies people will adapt to and what other companies will hold on too. Your best bet would be to learn what you can, all the while you’re keeping in mind what’s transferable and what’s just a trend.