>>35893524anon, it's in the same position as Ranger was in, a next-gen game made for the new hardware that the eventual Gen VIII game will run on, containing a brand new pokémon from said coming Gen VIII game.
Last I looked, this shit ISN'T running on 3DS, which means it ain't Gen VII. Also the fact it's made by Game Freak in-house and set in a region they originally conceptualised is making it mainline. But it is still a spin-off at the same time, when they confirmed it won't follow the usual core mechanics, like most the other spin-offs don't when it comes to recruiting new pokémon.