Once you transpile the TS, you have standardized ECMAScript. Want to stop using TS? No problem. Just delete your TS files and work from your JS files.
And, beyond that, TS is intended to be a superset -- never incompatible, just "extra".
Finally, you can use TypeScript the same way Flow is used, through comments.
Tying yourself to TS isn't really something you can do, and there's zero risk in using it. You can always throw it out later.