AI is already poisoning itself. There were experiments where they tried to expand LLMs by feeding them synthetic content generated by LLMs. It turned to complete shit.
Now when they scrape the web, they are ingesting synthetic content, unable to filter it out, and it's damaging their models. Going forward, all "new" content will be suspect. Even published material in books, magazines, and other physical media is now being poisoned by LLM generated content. To expand, they'll have to scrounge the libraries of the world, digitizing anything they can find that hasn't already been digitized. Much of this will be of limited value and it won't take long for it to run out.
Due to LLM poison, LLMs might actually now be near their apogee.