It's probably not gonna happen. (Your source is most probably wrong) I can say this, because, typescript emphasis heavily on strongly typed variables, which is something Facebook Open Source already offers with React-PropTypes and flow.js. They would rather use something they have developed on their own than using something that was developed by a different team (& organisation).
( Tags: Typescript is awesome, React is awesome, flow is awesome, proptypes is awesome. Hoping no one is offended.)