https://www.gamespot.com/articles/pokemon-ultra-sun-and-moon-dev-explains-which-game/1100-6454190/

Elsewhere in our interview, Game Freak explained why Pokemon Ultra Sun and Moon aren't coming to Nintendo Switch and said how the upcoming games are helping the development of Pokemon for Switch. Look out for more from the interview soon. The games, meanwhile, launch for 3DS on November 17, featuring an "alternate" story and some new Pokemon. If you're still playing the base games, however, you can check out all the free Pokemon and items you can get in Pokemon Sun and Moon right now.