You're describing an arms race, which makes me wonder if that's part of the path to AGI. Ultimately the only way to truly detect a fake is to compare it to reality, and the only way to train a model to understand whether it is looking at reality or a generated image is to teach it to understand context and meaning, and that's basically the ballgame at that point. That's a qualitative shift, and in that scenario we get there with opposing groups each pursuing their own ends, not with a single group intentionally making AGI.