I would definitely be surprised if people who've been asking good questions on StackOverflow so far would suddenly ask them elsewhere, since part of what makes a question good for StackOverflow is that it cannot be easily answered elsewhere. E.g. MathOverflow is a forum for mathematicians to talk about their research, they're unlikely to use LLMs for that anytime soon.

So fewer people asking questions doesn't mean the community is dying, it might very well be a sign that they finally succeeded in their war to keep everyone else out.

Probably bad for the company milking the community for profit, though.