Rowling usually maintains pretty tight control over her work, though. In fact, this quote is part of the article, from that same guy:

“And I think maybe there’s some other creative possibilities within this world, but J.K. Rowling controls all of it and is not going to let anyone else come play with her toys. And that’s her right and is obviously very profitable for her. So that’s what we get.”

I think this means that their ability to subvert is limited. They’ll be stuck with doing stuff Rowling agrees to, which I would expect means we might see a “more diverse” main trio—she’s signed off on a black Hermiome before—and we might see the insertion of extra gay stuff for Dumbledore, or maybe some Jewish students, or anything that plays into her habit of grafting in extra brownie points things that didn’t really exist in the original versions. What we probably won’t see is wholesale departure from or subversion of major plot points and character traits. We won’t get “actually, James Potter was kind of a douche,” we won’t get trannies, etc.