The SEO garbage has been poisoning the search for years. Even before the chatbots it got to the point when most top results are crap. The LLM's can surely make it much worse, though.
Ultimately, I would like to see more about the other side. If generative AI can make blog spam, then I think it can recognise blog spam. How far are we from implementing a reliable filter of useless spam sites from search results? I don't expect Google has a monetary incentive for this, but maybe someone else does. But from my story above maybe "search" is a thing of the past and for functional queries, we will just talk to the gatekeeper. Reading the actual words written will only be for leisure.
This is too much of a temptation for the SEO scum to resist.