I can see the road you're traveling, but there are a couple of hitches in your scenario: first, what a writer writes best isn't a matter of his or her choice, or at least not to a large extent. Mr. King could choose to write YA romance or dystopia, it's true, but chances are he wouldn't do it nearly as well as he can write what is naturally within his wheelhouse. In my opinion,
Finders Keepers is a good example of that. It is a good book, make no mistake, but the places where he tries to hew closely to crime fiction norms are weaker than the places where he goes with his strengths: dialogue, character building. I can see why he's done what he's done, as far as trying a new genre; after 50 or so years of writing, a challenge is refreshing! I remember Mr. King himself talking (well, writing, but I always 'hear' his non-fiction stuff in my head like he really was talking to me
) about how he and Louis L'Amour could both sit by a beautiful pond and come up with two completely different stories (I think he said Mr. L'Amour would start a story about ranchers and water rights and he himself would write about tentacles coming out of the water--lol). We are how we're wired.
The second flaw is in assuming that a writer can successfully write to a trend. Think of the life arc of a manuscript: for many authors, the first draft can take up to a year. I understand that Mr. King is more prolific, and I think I remember reading something about him saying that he gives himself around three months for a first draft (thought that might have been Joe Hill). So. Three months for that. Then a good writer lets that draft lie fallow for a while--anywhere from a few weeks to a few months. It has to become a stranger to you before you have the objectivity to start working on it. So then you have a second draft. Then a third (on average). THEN the book is ready to send to your editor. Depending on their their schedule, there might be a lag before they can take it up. If there isn't a lot of editing to be done, you might get away with one more set of edits... but probably not. You're now at least a year into this book, maybe a year and a half. Then it goes to copyedits, marketing, cover, and omg! you need a new author photo. At this point, you're getting close to production. For someone like Mr. King, maybe things are sped up a bit; littler guys get put in the queue and your stuff gets done when it gets done, in between 'bigger' drops. Bottom line: it might be two to three years before the germ that went floating around in your head is a published novel. If you've written purely to satisfy a trend, you'd better pray to god that the trend hasn't changed. It likely has. See a lot of bondage books hitting it big lately? How about vampires? Shapeshifters? Dystopias? Fairy tale reboots? Zombies are waning, ghosts ascendant, but that couldn't have been predicted--it might just as well have been alien garbage cats that hit the public fancy. My point is that writing and publishing a book takes time, and no one can tell what is going to be 'hot' from one season to the next. How it works at the best of times is someone writes something they're passionate about, something they really love, and if they're lucky other people catch that passion and run with it. Sometimes it carries some other authors along (Roth's
Divergent series coat-tailed on
Hunger Games and
Twilight), but they have to come out of the gate fairly quickly behind the trend--chances are, they were already working on something similar when the first book 'hit'. The only way to quickly capitalize on a trend is to self-publish, and that comes with it's own issues.