I was thinking the exact same thing last month[1]! It's really interesting what the implications of this might be, and how valuable human-derived content might become. There's still this idea of model collapse, whereby the output of LLMs trained repeatedly on artificial content descends into what we think is gibberish, so however realistic ChatGPT appears, there are still significant differences between its writing and ours.
[1]: https://www.glfharris.com/posts/2024/low-background-lexicogr...