(I work at Meta)
It’s only once the business is having a cash crunch or will no longer need to hire competitive candidates that they start letting people go without severance.
Tell that to Elon Musk and Twitter employees.
This will also give them data on which employees aren't using AI enough, and then they'll be PIP'd or let go.
These models already have the skills that humans were using them for, so either by training the models to use subagents or simply inlining the work done by the AI, you have a much easier time training the model to perform tasks from a human-distribution. The humans have done the work of making the human-distribution look more like an AI distribution.
If it is as you say, then eventually the house of cards will crumble. Then we can finally go back to work and quit being inundated with needing to use AI for everything.