AI most definitely is a coworker already. You do delegate some work for which you previously had to hire humans.
(Old study, I wonder if it holds up on newer models? https://arxiv.org/pdf/2402.14531)
My worst experience of co-workers (and in contract work, customers) is when they treat me the way I used to treat ChatGPT. If I can make sure I myself am never like that, just by training myself to different behaviour through my use of the infinitely patient LLMs, all the better. :)