- Which might be a different matter: of specifically SE declining. (A very different, and long-running, tragedy, but one that began long before the current AI boom and prompted by very different, non-technical issues.)

- That said, surely traffic will decline for Q&A sites. "How do I connect tab A into slot B" is something that people are likely to query LLMs for; the response will surely sound authoritative, and could be even correct. That's definitely a task where LLMs could help: common questions that have been asked many times (and as such, are likely to be well-answered in the human-made training data). A 20001st question of "how do I right-align a paragraph in HTML" has not been posted? Good. Rote tasks are well-suited to automation. (Which, again, brings us back to the issue "how to distinguish the response quality?")

I upvoted your comment because I'm afraid you may be correct. I say, "afraid" because I can remember the day when a member of my team was fired for copy pasta from SO with little, if any understanding, into "production" code.

The problem, of course, is that this might work once in a while for low hanging fruit, until the web inherited things like DICOM and we now have medical imaging in the web browser (I've heard in Apple Vision Pro), where robotics implies the price of unforeseen bugs is not accidental death or dismemberment of one patient, but potentially many.