I'd imagine that when the 80% of less productive time is automated, the market doesn't respond by demanding 80% more output. There's just 20% as much work either making this a part time job or more likely a much smaller workforce as the number of man*hours demanded by the market greatly reduces.

Scope will increase.

Good accounting teams will have more time and resources to do things like identify fraud, waste, duplicated processes, etc. They will also have time to streamline/optimize existing practices.

Good teams will earn many multiples of their cost in terms of savings or increased earnings.

There may be increased competition for the low-cost “just meet the legal compliance requirements” offerings, but any business that makes money and wants to make more will gladly spend more than the minimum for better service.