The ECMAScript standard did consider transpiled languages - for example, by incorporating concepts from CoffeeScript like classes, destructuring, arrow functions. For sure they're considering ideas from TypeScript.

I'd imagine some advances in the CSS specs are influenced by concepts from traspiled languages such as Sass, for example, variables and nested selectors.

I don’t follow this logic at all. An idea can be rained by virtue of it first being included in a preprocessor? postcss would like to have a word.

was just thinking this. work on a variety of complex webapps across multiple frameworks and you'd never catch me dead using css-in-js or a preprocessor.