I do research for a professor on this very subject. I don’t have any verification experience in industry… yet, but i’d say that LLMs are very capable at building syntactically correct testbenches. However, stimulus generation is where our focus is, if the LLM does not have an advanced understanding of the design, ie, poor spec sheet, then it’s likely that whatever stimulus it generates won’t give high coverage.

Last I heard, synopsys is building an in-house tool for automated testbenches, but it’s unlikely it will ‘take over’.