I only see that happening if TC39 pulls a PEP 3107 [1] approach and adds type annotations as optional part of the JS language directly that browsers don't need

I only see that happening if TC39 pulls a PEP 3107 [1] approach and adds type annotations as optional part of the JS language directly that browsers don't need to understand and can ignore but should parse. The Typescript format of type annotations is much more convenient than the JSDoc style (and think Typescript surpassing Flow is in part because of that; among several other reasons), so there likely will always be people wanting it. At that point a PEP 3107 approach would both mean a lot less need for Typescript and also a lot more use of Typescript-like type annotations. Deno's odd choices made on V8 performance issues (failures) also does not look to implicate a trend so much as Deno making some interesting choices. (There too a PEP 3107 approach would have helped them as the performance issue they were trying to fix was type stripping as V8 itself doesn't today have any reason to performantly type strip TS-like annotations, but of course that would change tomorrow if TC39 made that a first class citizen of the JS parser directly.) [1] https://www.python.org/dev/peps/pep-3107/ https://www.python.org/dev/peps/pep-3107/