From passive listeners

Have you tried speaking with GPT-4 with voice-mode activated and a simple prompt?
If so, you'll understand the number of use-cases possible: teacher, salesperson, HR recruiter, project management, knowledge-base, interpreter, ...

AI agents with access to personal and company knowledge are already on the market.

Companies such as Twin.so and Lindy AI are offering digital clones of human office workers that can complete tasks. These tasks can, of course, include conversational ones.