From Bulbanews, your community Pokémon newspaper.
To be released November 17
The Pokémon Direct presentation announced Pokémon Ultra Sun and Ultra Moon for Nintendo 3DS. They will be released simultaneously worldwide on November 17, 2017. They are set in the world of Pokémon Sun and Moon, but have a different storyline.
Two new Pokémon forms appear in the world of Pokémon Ultra Sun and Pokémon Ultra Moon. As noted by the official site, they are reminiscent of the Legendary Pokémon Solgaleo, Lunala, and Necrozma. Notably, the official site avoids explicitly calling these Pokémon those names.
The games are said to “feature Pokémon that didn’t appear in the original versions”.