> they things they believe in are unlikely to happen.

Sorry, but most times I've talked to someone who says this (about AI completely replacing humanity), they don't have anything to say about why it's unlikely to happen other than:

- "well, it's just such an extreme outcome, it must be improbable"

- "humanity has survived near scrapes with extinction before"/"all the previous doomsday predictions have been wrong"

There is a cliche that all teenagers deep down believe that they are invincible. It seems to me that humanity is still a teenager in this respect: We don't take seriously the possibility of our own extinction. While one might think that the invention of nuclear weapons would serve as a wake-up call, if anything it has done the opposite.

I'm willing to hear arguments besides the two above, if you have them. (And to be clear, being replaced by AI doesn't necessarily mean being replaced by LLMs in particular. They are a relatively new development.)