> we can just agree to disagree
For what it's worth, Searle is a naturalist (so he thinks brains are "just" meaty machines) and he would also disagree with you.
> For example, is there any specific, measurable thing that you expect a future AI system absolutely will not be able to do?
Not sure how you'd measure this, but I think sentience is most likely unachievable by AIs (at least how we're building them now). This is not without controversy, as while Roger Penrose would agree with me, David Chalmers would not. I'm not actually sure when Chalmers pivoted on his stance (haven't read him much since undergrad) because he was a bit more hardline in the early 2000s[1].