Kind of depends how hard the studios want to fight on this, but I get the sense that they can just take foreign series and dub them for a while.
As for ChatGPT: ChatGPT is not competent at writing substance. ChatGPT excels at superficial basic structure; the kind you learn on the first day of high school English. Those who have tried using ChatGPT to write fiction have discovered that every story follows the same simple pattern, and it always skips over the most important part of the story (i.e., the part that writers would actually need help with) to skip straight to the conclusion where everybody lives happily ever after.
So ChatGPT might help a student with the bones of their creative writing assignment. But it and its LLM ilk will never be a force in Hollywood; that would require a better type of AI that is actually capable of substantive understanding.
I very recently tried to get ChatGPT to generate Fritz Leiber style stories, and it would always end with some trite moral or a "bad" character having a change of heart, even after repeatedly asking it to not do that.
It's a really good tool for brainstorming, though.