Ummm... You do know that you don't have to use Babel to use JS, right? ES5 is here, it was here then, and it works very well. It might have some pointy ends, but they are very well documented at this point.
Yes, of course, unless you had invested a lot into React/JSX, and Babel is the only "official" way (documented and blessed by Facebook) to run React and JSX in production.