Nobody disputes that TypeScript is open source, but there’s still a vast difference between a single open-source implementation and a specification that’s suitable for standardization. The implementation inevitably has bugs, and there needs to be a way to decide which bugs are actually “features” that other implementations will need to emulate.

(Here’s the specification for ECMAScript, for example: https://tc39.es/ecma262/)

To be clear, I am not bashing Microsoft here—just pointing out a reason that TypeScript can’t be declared “the next version of JavaScript”, which is the context of this thread.