I'm sort of surprised I'm not seeing any modernized dynamic scripting languages coming out lately, despite the general trend towards static languages. A fast dynamic language, with a day-one concurrency story, and some other key feature that pushes it ahead seems possible to me. (I dunno, maybe a nice story for binding to Rust instead of binding to C at this point could be enough to lift a language off?) I don't see any reason why dynamic scripting languages as a category couldn't do that. The ones we have now don't, not because the category makes it impossible, but because by the time that was desirable they just had too much baggage, and are all still struggling with it even a decade after they started.

What are examples of those semantics? I'm guessing rebindable functions (and a single function/variable namespace), eval(), and object members available as a dict.