What is an exponential growth curve of a chatbot supposed to look like? The endpoint is being consistently indistinguishable from a human on the other end. Once that is achieved, I don't see how you get even better than human at generating text. You can certainly get faster and generate a lot more text than a human, but computers have been able to do that already for decades.
I'm trying to think of what this author here envisions happening because an AI writes a story about doing bad things. Very good stories about human extinction have existed for a long time and have not resulted in actual human extinction. When I think of texts that seem associated with significant world historical changes, like the New Testament, Magna Carta, Declaration of Independence, it seems there was quite a bit of event context that was important, and it wasn't the sheer quality of the text itself that impacted history.
Similarly with art. Is Videogen-4 going to be able to create a synthetic sequence of image frames with an audio track that is "exponentially" better than Casablanca? What would that even mean? The quality of art is completely subjective. There is no quantifiable measure like transistor density that can get X times improvement. No film has the power to cause human extinction and neither do great filmmakers.