Regardless, the human generating and publishing these images is obviously responsible to ensure they are not violating any IP property. So they might get sued by Disney. I don't get why the AI companies would be effected in any way. Disney is not suing Blender if I render an image of Mickey Mouse with it.
Though I am sure that artists might find an likely ally in Disney against the "AI"'s when they tell them about their idea of making art-styles copyright-able Being able to monopolize art styles would be indeed a dream come true for those huge corporations.
So in effect, they are pitting Disney's understanding of copyright (maximally strict) against that of the AI companies (maximally loose).
Even if it's technically the responsibility of the user not to publish generated images that contain copyrighted content, I can't imagine that Disney is very happy with a situation where everyone can download Stable Diffusion and generate their own arbitrary artwork of Disney characters in a few minutes.
So that strategy might actually work. I wish them good luck and will restock my popcorn reserves just in case :)
The problem I see though is that both sides are billion dollar companies - and there is probably a lot of interest in AI tech within Disney themselves. So it might just as well happen that both sides find some kind of agreement that's beneficial for both of them and leaves the artists holding the bag.
Go to a baker and commission a Mickey Mouse cake. Is that a violation if the bakery didn't advertise it? (To note, a bakery can't advertise it due to trademark, not copyright. Right?)
For that matter, any privately commissioned art? Is that really what artists want to lock away?
That's actually a tricky question and lengthy court battles were held over this in both the US and Europe. In the end, all courts decided that the image result page is questionable when it comes to copyright, but generally covered by fair use. The question is how far fair use goes when people are using the data in derivative work. Google specifically added licensing info about images to further cover their back, but this whole fair use stuff gets really murky when you have automatic scrapers using google images to train AIs who in turn create art for sale eventually. There's a lot of actors in that process that profit indirectly from the provided images. This will probably once again fall back to the courts sooner or later.