The term "self-play" is particularly appropriate here - masturbatory nonsense. AGI is a myth. Future generations will pity it the same way we do flat earth. We still lack a scientific method to transpose thought into optimization / computation. Deep learning and A.I. as it exists today are algorithms that optimize a loss function. Thinking and concepts and language and semantic meaning are much more complicated than game-like scenarios where loss is evident. They self-contradict, they evolve, and they don't have obvious optimization criteria. The best we'll get is an "operational" intelligence that can't really consciously think, but only seems to by how it operates (Turing test). Until we achieve a meta-cognitive understanding of thought, machine consciousness will remain out of reach.