I'd like to propose a counterargument:
Assumptions: Theory of evolution is true. The primordial single-cell organism from which we all evolved was not conscious, but rather just a biological machine. Humans are conscious.
Deduction: Somewhere along the line between the primordial single-cell organism and a human being, there was a transition from non-consciousness to consciousness, and the only [*] factor in that transition was the complexity of the nervous system.
Conclusion: Consciousness (or, "real" intelligence) arises from the complexity of a machine. AI can, in principle, become conscious.
Yes, we know how AI works, because we built it. But why would that make consciousness arising from a sufficiently-complex statistical model impossible?
[*] as per apendleton's comment, I have made mistake here: complexity is not the only factor, but is a necessary one in creation of consciousness.