Yeah but competitive battlers are the minority among Pokémon players. It's a given that competitive battling moves to the latest game, but there are still people who play the older games regardless.
Actually, even that scene doesn't have a direction yet. Most of the competitive battlers hack their Pokémon, and this isn't possible in the 3DS. And Smogon no longer has the head start they once did when they could test the moves and abilities in the Japanese version and port them to their simulator. It will be an era of discovery and everyone will start from zero when the games are released. Of course, hacked Pokémon could still be transferred from earlier games, but at least the new Pokémon won't be able to be hacked.