The thing is: it's fucking hard to do good AI generated content, because AI is dumb as fuck. It's like trying to draw with a pen that keeps failing, or knitting while using boxing gloves, or trying to make a nail work as a screw.
The day AI generates perfectly anatomically coherent pictures, with correct genitalia and other details, without taking hours/days inpainting or editing shit until it's acceptable, is the day artists for porn are going to be a second thought.
Nothing will beat you being able to create your wildest desires with a few descriptive words and the push of a button.
It will never truly completely end human content though, there's some things that a machine will never be able to do like we do (at least in a couple centuries yet), even tho we are machines too, biological ones, but nonetheless...