Most technological advances had the purpose of replacing workers. 500 years ago you needed 80-90 farmers for every 100 people in your community. 100 years ago you needed 30 farmers, and today you need 4. That profession lost 95% of its workforce over the past few centuries because of technological advances.
Today the US worker is about 3x as productive as we were 100 years ago. Along with more people entering the workforce (mostly women) this productivity boost allows us to consume about 6x as many goods and services as the average American did 100 years ago. It also means that for every 100 jobs in 1924, 70 of them were displaced by technological advancement. In their place came 170 new jobs that didn't exist 100 years ago.
AI is likely one of the significant drivers of productivity improvements in the next century. It wouldn't be surprising to see 60-80% of all today's jobs being lost over the next century. It's what happened last century. The only questions are whether new jobs will be created, and whether we will start consuming 6x more goods and services 100 years from now than we do today. The answer to those questions will determine how many people are still employed in the future.
If we didn't start consuming more last century, worker participation rate would be 20% today. The same is very likely true in the upcoming century. Either the working class in 2124 will live lives comparable to the upper middle class today, very few people overall will be employed, or somewhere in between.