Doubtful. To be honest I'm expecting a narrative prequel if anything, because that's the only thing they haven't done yet. We've had third versions, sequels, DLC expansions, and alternate variations. A prequel is just about the only thing they haven't tried and, for all of Game Freak's flaws, since the fourth generation ended they at least haven't given themselves over to direct repetition when it comes to releasing content that should have been in the original games.
I suppose you could say Legends Arceus is a prequel to the Sinnoh games, but as far as I'm concerned until we get another game in that style it's a spinoff. No matter what Game Freak might try to claim. They think the Let's Go titles are main series titles too, which is rubbish. So...