TC39 still has scars from ES4 which tried to add optional typing (and is the only "lost" ES standard that browsers never implemented).
My hope is that since then we have examples like Python's PEP 3107 [0] that help make sense as where a TC39 proposal could move forward: encourage browsers to AST parse type annotations, and ignore them by default; leaving the actual semantics still to tools like Flow and Typescript until there is a better convergence in semantics and/or browsers have greater needs of specific type annotations.
I've had the same thoughts. Seeing what happened with CS, getting too involved in the TS ecosystem seems like setting yourself up for some future pain if what you're doing will be long-lived.
I actually think we'll see more advances in webassembly first, though. It won't surprise me if Java makes a comeback for the frontend.
I've seen a few proposals around but it seemed that they were are stalled.