I'm actually going to venture a serious guess here...
A couple weeks ago, Brandon Sanderson announced that Apple TV had bought the rights to make a trilogy of Mistborn movies and a Stormlight Archive tv series. Best of all, Sanderson is being given complete creative control over them, so just from that they're almost guaranteed to great. Between The Witcher, Rings of Power, Wheel of Time, and the last few seasons of Game of Thrones, we've been hurting for a good new fantasy series for a long time now. I theorize that Sanderson's movies and show are going to usher in a new wave of fantasy appreciation. About time too, since all we seem to have been getting lately is superhero and scifi junk. But with that new surge of popularity, people are going to decide to try their hand at making their own epic high fantasy stories. Most of them are going to go straight to Kindle, but enough are going to make their way to sites like this and Royal Road that people are going to notice them. That will cause even more aspiring authors to try out the genre, and slowly but surely it will push litrpgs out of the spotlight.
If I were to take it a step further, I'd say that for a while, generic high fantasy is going to be the big thing, but it won't take long to settle into a niche, just like what happened with litrpg. People aren't going to want to sift through the mountains of trash that sites like this always accumulate when they could just go to Barnes and Noble and pick up something that was edited and published by professionals. The things that blow up online are usually things that you can't get anywhere else. I don't know what that niche is going to be, though. Hard magic systems sound like a pretty safe guess since this wave is going to originate from Brandon Sanderson, but it'll probably find an even nicher niche than that before long. Maybe epic high fantasy adventures with hard magic systems based around people projecting their subconscious minds into the real world through lucid dreaming?
Or maybe it could be pirates.
