This just signifies the end of the era of "fashion model" as a lucrative career choice?
I'm not a fan of AI getting used in marketing/advertising at all. But that's mostly because I find most of it can still be picked out from reality. When they try to create new animated characters or mascots, for example? The AI attempts I've seen, so far, just have this set of features that clue you in that they aren't original drawings by a person. With people, they may be getting pretty good at starting with an AI generated person and letting a real artist Photoshop it to fix it/clean it up so it passes as real. But mostly, we're still used to seeing the people with odd numbers of fingers or toes and other AI mishaps.
When they get this honed to perfection? Yeah, it's not going to make a lot of sense to pay real humans to model clothing for your average sale flyers or online ads. The value will still be there for a popular celebrity figure to wear something in an ad, because then you're buying that association with their fame. But I think most models should come to grips with the idea the gravy train is reaching the end of the line.