TC-39 is kind of lame at the moment. I can’t imagine they will stay this lame forever. There are some reasonable voices inside TC-39, so even thought currently the lame voices at the committee are more powerful, that could change at any moment.

It’s moving slowly, but I think it’s almost inevitable. Type annotations are generally gaining or maintaining their already widespread popularity, and bringing them into the language syntax would just be an acknowledgment of that fact. I think the only thing that might hold that back is the proposal’s commitment to non-TypeScript use cases, which while magnanimous is a huge opportunity for the kinds of bike shedding that might tank a proposal like it.