Right now storytelling and themes will still be safe. The AI will have some difficulty giving work real meaning, and I'm not saying that because I am some kind of human elitist - I still believe AI will wipe out most of the art industry. But how do you "train" an AI to write a narrative handling how to deal with a romantic comedy where each character handles love in a different way, for example, with consistent characterizations and character growth over many many chapters, and resolving in a chaotic final scene where everyone's arcs resolve at once? Certainly it might be possible but it is not a trivial problem the way generating "Elon Musk as an Astronaut" already is, or using AI Dungeon to roleplay as a wizard or write a beautiful description of a house.

As above however, art that exists purely to be descriptive or entertain will not be safe at all however. An already difficult profession to break into will be made tougher still to make a living from.