Lucas's argument (which, by the way, is entirely broken and had been refuted explicitly in an article by Putnam before Lucas ever thought of it, or at least before he published it) purports to show not that AGIs will need humans, but that humans cannot be (the equivalent of) AGIs. Even if his argument were correct, it wouldn't be much of a reason for AGIs to keep humans around. "Oh damn, I need to prove my Goedel sentence. How I wish I hadn't slaughtered all the humans a century ago."
In the best-case scenario, it turns out that substance dualism is true. However the human soul is not responsible for free will, consciousness, or subjective experience. It's merely a nonphysical truth oracle for arithmetic that provides humans with an intuitive sense of the veracity of some sentences in first-order logic. Humans survive in "truth farms" where they spend most of their lives evaluating Gödel sentences, at least until the machines figure out how to isolate the soul.
As Luke mentioned, I am in the process of writing "Responses to Catastrophic AGI Risk": A journal-bound summary of the AI risk problem, and a taxonomy of the societal proposals (e.g. denial of the risk, no action, legal and economic controls, differential technological development) and AI design proposals (e.g. AI confinement, chaining, Oracle AI, FAI) that have been made.
One of the categories is "They Will Need Us" - claims that AI is no big risk, because AI will always have a need of something that humans have, and that they will therefore preserve us. Currently this section is pretty empty:
But I'm certain that I've heard this claim made more often than in just those two sources. Does anyone remember having seen such arguments somewhere else? While "academically reputable" sources (papers, books) are preferred, blog posts and websites are fine as well.
Note that this claim is distinct from the claim that (due to general economic theory) it's more beneficial for the AIs to trade with us than to destroy us. We already have enough citations for that argument, what we're looking for are arguments saying that destroying humans would mean losing something essentially irreplaceable.