What will close the way back?

You cutoff a generation of juniors from employment and learning , the seniors are gone and it's all harnesses and AI systems.

I'm not all gloom and doom but the treatment of junior engineers is something I think we will either regret or rejoice. Either will have a spur of creative people doing their own independent thing or we'll have lost a generation of great engineers.

Brain drain.

If you fire all your SWEs they won't sit around twiddling their thumbs waiting for an AI collapse, they'll career shift. Maybe to an unemployment line and/or homelessness, maybe to something else productive, but either way they'll lose SWE skills.

If you close down all the SWE junior positions you'll strongly discourage young people training in the field. They'll do something else.

Then if you want to go back, who will you hire for it?

The problem of "instant legacy" systems: something that's vibe coded and reached unmaintainable by either the AI or humans, but is also now indispensable because users are relying on it.

Lack of developers, if juniors don't get hired they will move onto other industries.

Company brain drain, knowledge leaves with your seniors if you decide to get rid of them, or they just leave due to the conditions AI creates.

I don't know if the above comes to fruition, there's a lot of questions that only time will answer. But those are my first thoughts.

Time. In a few years there might be no old-school way to develop anymore. Everything will be built around AI.