Can someone explain to me the migration path towards ES6 and syntax like this? This isn't syntactically valid ES5, so is there a reasonable path to making the b

Can someone explain to me the migration path towards ES6 and syntax like this? This isn't syntactically valid ES5, so is there a reasonable path to making the browsers run ES6 directly? If I just include it in a <script> tag directly, it'll throw syntax errors in any non-es6 compliant browser. So I'd have the transpile, and send down the es5 version of the code. But if I'm transpiling, what's the point? I still have a build step, so why use ES6 over another compile-to-js language? The eventual promise, that years and years and years from now, all the non-es6 compliant browser will be dead, so I can send down the es6 code directly?