If Node.js can run TypeScript files directly, then the TypeScript compiler won't need to strip types and convert to JavaScript - it could be used solely as a type checker. This would be similar to the situation in Python, where type checkers check types and leave them intact, and the Python interpreter just ignores them.
It's interesting, though, that this approach in Python has led to several (4?) different popular type checkers, which AFAIK all use the same type hint syntax but apply different semantics. However for JavaScript, TypeScript seems to have become the one-and-only popular type checker.
In Python, I've even heard of people writing types in source code but never checking them, essentially using type hints as a more convenient syntax for comments. Support for ignoring types in Node.js would make that approach possible in JavaScript as well.
It's interesting, though, that this approach in Python has led to several (4?) different popular type checkers, which AFAIK all use the same type hint syntax but apply different semantics. However for JavaScript, TypeScript seems to have become the one-and-only popular type checker.
In Python, I've even heard of people writing types in source code but never checking them, essentially using type hints as a more convenient syntax for comments. Support for ignoring types in Node.js would make that approach possible in JavaScript as well.