Given that React is already heavily invested in Flow types, there would be _some_ form of rewrite.
And like I said, Flow is providing sufficient benefit for the React team right now, and their focus is on expanding React's capabilities. Changing type systems is not on their radar as far as I know.
Oh— can you point me at a file in particular? I had a look around the codebase and didn't see anything but plain JS. Might have been looking in the wrong places.
And I certainly get your point. However I wonder if they'd consider community-contributed TypeScript declaration files to the official repo as they wouldn't cause conflicts with the Flow system—
As for the TS typings, there's been lots of agitation from people asking them to be officially included and shipped with React. But, again, the React devs themselves aren't TS users (that I know of), and so they don't have the expertise to write and maintain those typings. Better that they be left over in DefinitelyTyped for the community to maintain.
(I'm a Redux maintainer, and I feel exactly the same way about the typings for React-Redux. I don't have any actual TS experience myself yet, and I couldn't do anything useful in regards to the React-Redux typings. Plus, I've got far too much else on my plate to worry about those.)
And like I said, Flow is providing sufficient benefit for the React team right now, and their focus is on expanding React's capabilities. Changing type systems is not on their radar as far as I know.