Who would take over after she died?
I think one possible candidate might be Anthony Horowitz. His popular Alex Rider series was just getting started (the second book Point Blanc was published in 2001), and he had previously written a sort of proto-Harry Potter story in 1988 (Groosham Grange, which was an awesome read by the way) and as well as a sequel in 1990 (the Unholy Grail, which was also pretty good). I'm not sure how he would have tackled the rest of the Potter books. A lot of his material could be quite dark and twisted, so I could see the later Harry Potter books being much darker than IOTL (and Rowling wasn't above touching on some pretty dark material). I can also see a bit more scathing satire, especially with regards to the Ministry of Magic.
Of course, if Horowitz ends up writing the Harry Potter books that might mean that he has to drop the Alex Rider books, or at least put them on the back-burner, which is going to make the anachronisms either worse (the books were written over a period of thirteen years, but the story takes place in the course of just over a year, and the pop culture references are kept up to date). Of course if the Alex Rider books get less attention, we might be able to avoid the abysmal film adaptation. Alternatively he might not re-continue the Diamond Brothers series (I haven't read enough to say if that's a good or a bad thing, but I enjoyed the first one).
This has the potential to be either one of the best or worst things to happen to my childhood.