The fact it's now super easy to generate content and copy others means people won't be motivated to create many original pieces.

Which in turn means less material for the AI to train and copy, and at some point, it will become obvious it's recycling variations of the same initial training set.

One example where this is not just a theoretical: SEO people quickly figured out they could ask AI to edit an article and it would rank better for all keywords selected, so they did. But the AI is just mixing snippets from other sources with their own quirky language. So now everyone's pages look the same, and provide no original material, so they are back to ranking lower because they're all fighting with the same amount of information.