Also, you seem to reach the conclusion that there will not necessarily be any individuality in the 'post-AI' future society, but then give several good reasons why such individuality may persist. (namely, speed of light, locality of physics)

Yes - it's a matter of degree. Humans are isolated to a greater extent than I expect AIs to be. Also, the word "individual" means (I think) non-divisible, which AIs probably will not be.

I agree, the term post-AI is confusing. I'll remove the 'post'.