"[Engineers] tend to overestimate what can be done in the short-term and underestimate what will be done in the long-term." I'd expect level 5 autonomy to be s

"[Engineers] tend to overestimate what can be done in the short-term and underestimate what will be done in the long-term." I'd expect level 5 autonomy to be slow, because level 4 delivers 80% of the benefits for 20% of the cost. BUT "never" seems crazy unless you've got a very pessimistic outlook on humanity's medium-term future. Other than extinction or the collapse of civilization, what could cause it to "never" happen?