I believe the idea is to not stop hiring juniors. Instead it's to replace anybody that commands a high salary with a team of cheaper juniors armed with LLM's. The idea is more about dragging down average pay than never hiring anybody. At least for now.
And then all those unemployed seniors with extensive domain knowledge use AI to speedrun the creation of competition and you need to spend $$$$ to buy them out and shut them down. Solid idea.