I disagree with the number 100. It is not a reasonable number with respect to current AI capabilities.
If the cost of digging ditches goes down, companies will be apt to dig more ditches. I've seen many projects worth $100k-$500k but they weren't pursued because the cost in salaries was higher.
I don't think companies are generally well run to let go of unnecessary people efficiently. At least one place I've worked at had, by my estimates, $100m salary of unnecessary people employed. It didn't matter, the business has revenues of $100b yearly, so it's a drop in the bucket.
If a solopreneur can buy an excavator, the corporate developers will get them too.
I do think it will be easier for very small organizations to compete than it was previously - which is great - but let's not fool ourselves that big companies won't maintain some competitive advantages.