I suppose it's more likely to be literary fiction, or aimed in that direction. Story of how a pennyless single mother writes in secret for years and finally finds success, and a new lover, perhaps?
It's a big risk she's taking, because in some ways children are an uncritical audience. They either like it or they don't, and if they do, they'll clamour for more, more, more. But adults are a different thing altogether, especially in cases such as this. There will be those that think she has all the success and monetary reward one author ought to have, and that it isn't fair to try for more. Others will applaud her efforts for trying, even if they think the result is pretty feeble. Some will give an honest opinion of the work. No doubt there'll be the one nasty review on Amazon.
Whatever it turns out to be, it will be interesting. I suppose all the Hogwarts fans who are now young adults with salaries to splurge will buy a copy out of a mixture of curiosity, hope and loyalty. The reviewers will be sharpening their pencils. The publishing world will watch with interest. I note she has gone to a new publisher and that her relationship with Bloomsbury was "tempestuous" acording to one report I read.
Sigh. Well, I just wish I had that much clout.