The million dollar (perhaps literally) question is – could @kentonv have written this library quicker by himself without any AI help?
But what if you only need 2 kentonv's instead of 20 at the end? Do you assume we'll find enough new tasks that will occupy the other 18? I think that's the question.
And the author is implementing a fairly technical project in this case. How about routine LoB app development?
This is likely where all this will end up. I have doubts that AI will replace all engineers, but I have no doubt in my mind that we'll certainly need a lot less engineers.
A not so dissimilar thing happened in the sysadmin world (my career) when everything transitioned from ClickOps to the cloud & Infrastructure as Code. Infrastructure that needed 10 sysadmins to manage now only needed 1 or 2 infrastructure folks.
The role still exists, but the quantity needed is drastically reduced. The work that I do now by myself would have needed an entire team before AWS/Ansible/Terraform, etc.
It’s an exaggeration I know, but you get the point.
Software is often not the bottleneck. If instead of 10 engineers you just need the one, the company will shed headcount it doesn't need. This might mean, for example, that instead of 10 developers and a software testing engineer, now a team changes to perhaps add testers while firing half of the developers.