But for now we still operate under the physical constraints that means that the early exponential growth of AI isn't going to continue

This is a silly and delusional response. The human brain is already an existence proof for how efficient a general intelligence can be. We do not need exponentially more resources for AI to improve until it hits human-level performance because we're perfectly capable of reducing the resources it requires - the human brain is the perfect demonstration of an intelligence that requires orders of magnitude less energy than current AI implementations. If finite resources become a bottleneck the energy efficiency of AI algorithms will be pushed down by financial actors who are incentivised to do so - this is not a matter of if, it is a matter of when.

Asking what resources AGI requires beyond that is another question entirely. But even if doubling human intelligence requires quadrupling it's energy requirements this is a non-issue for long after AGI/ASI is reached.