We don't know what JKR thinks of Depp these days. What we know is that she stated this on her website 4 years ago:
However, the agreements that have been put in place to protect the privacy of two people, both of whom have expressed a desire to get on with their lives, must be respected. Based on our understanding of the circumstances, the filmmakers and I are not only comfortable sticking with our original casting, but genuinely happy to have Johnny playing a major character in the movies.
www.jkrowling.com/opinions/grindelwald-casting/