Robert, I agree we shouldn't be overconfident, that many past predictions were bad, that my scenario is just one of many to consider, and that other big changes could also make big differences. But even so, it still seems we should try our best to think through each scenario that we consider, using all the best standard results from all relevant fields.
I'd be happy to share my 94K word book draft with you, and would seriously consider any specific critiques you might have. But there isn't much one can say in response to "we can't possibly know" or "surely things won't stay recognizably the same." Those seem to me to be conversation-enders, and I want to continue the conversation. We can't be trying our best if we just quit merely because we realize that eventually we must reach limits to our abilities to foresee. Instead, we should only quit when the complexity of the task exceeds our patience to work through the many relevant details.