There are already quite a few AI-written pieces on AO3! Although I think people are mainly just being experimental or messing around, or, like JOhn says, creating a ship fic with little effort.

I mean, yes, it's a hobby for the love of it, so I don't think it's going to take over, but people will use it and probably increasingly, for fic, particularly, because there's no rules and no editor to send it back and say, write it yourself, Bob, I can tell when you've fed it to an AI. Also, crack is a tradition.