The next mainstream Pokemon games have been revealed to be Pokemon Scarlet and Pokemon Violet and they are set to be released in late 2022 for the Nintendo Switch. The announcement was made by the company during their annual Pokémon Day celebration last February 27.
Due to the release and success of the spinoff game Pokémon Legends: Arceus and the remakes of Platinum and Pearl, nobody was expecting Gamefreak and Nintendo to release a new game so early. Not to mention that these are mainstream games that will be the 9th Generation.