If AI works the way you suggest then we've literally been here before and we know exactly how this goes.

When tractors came along, farmers became dramatically more productive. Were the farmers who did things the old way "forced" to buy tractors in order to stay afloat? Over time, sure. But this was in no way zero-sum. More products made it to market (literally), more of the workforce was able to shift away from manual labor, and society became much better off overall. The people who moved to cities made dramatically more money, and the farmers who remained made more money too.

Edit: this is literally on the front page right now: https://news.ycombinator.com/item?id=48775979

This is not a prisoner's dilemma in any meaningful sense, unless you just like being inefficient and wasting a bunch of human effort.

(I'm not convinced yet whether AI actually works this way or not. I'm just saying, if it works this way, the economic theory is well-developed and we can predict fairly accurately how it's going to play out.)