The essence of romance is true love: Girl meets boy. Obstacles arise. Love wins in the end. This theme, thankfully, never goes out of style.
What does is genre, the wrapping we package around each version of our love story.
If a story genre falls out of popularity, can a story be repackaged to sell?
My first WIP was a western. Spunky daughter needs to save the ranch. (I live on a cattle farm, so I was trying to write what I know.) My craft skills were rudimentary, but my overall story arc was actually quite good. I hope to revive it soon.
If westerns are not in vogue when I do, I could turn it into a sci-fi. (Think Star Wars. It's a western set in space.) Or possibly an urban fantasy. Same story, just different packaging.
But should I?