Many of the greatest writers haven't. Stephen King doesn't write epic romance and Nicholas Sparks doesn't write horror. Jerry Spinelli was known for his YA or MG works that were about social acceptance and even Stephenie Meyers stays in her lane in paranormal romance. But is it possible for an author to transcend genres successfully.
According to www.publishersmarketplace.com, JK Rowling is currently working on an adult novel. If she succeeds, she has bridged the gap of authors known for one style of writing completely changing what their skill set is. Are there others that have done this? Is it possible?