Placing bets on trends for the future: Gritty is here to stay, same as Dystopia for the rest of the decade at least. Grimdark is slowly going to meld into Viking Fantasy, yes. Show me a stereotypical Grimdark that doesn't have some semblance of a barbarian.
Flintlock Fantasy will continue to under perform, but like Steampunk, it will find a niche eventually. New Weird will continue to flourish, though maybe not at the rate it did with the early China Mieville, Mark Charan Newton, and Jeff Vandermeer. There's still Kameron Hurley and Mark T Barnes to champion the movement.
Fantasy Noir will continue to fly under the radar as a subset of UF, shelling out two or three major works a year one day. I think we're seeing our first this year with Dark Star by Oliver Langmead and The Dragons of Heaven by Alyc Helms.
Speaking of China influenced Fantasy, I'm still placing half my chips on Silk Road Fantasy. It's doing about as well as Flintlock I'd say, but there's actually a well of untapped potential to actually flourish. I dunno. Stuff like this (examining trends in literature) has always fascinated me. Love to speculate on how we got here and perhaps where we'll be headed next, though some weirdo could come and blow that train off its tracks any day.