The known first-party releases for the Nintendo Switch in 2020 includes Animal Crossing: New Horizons, Tokyo Mirage Sessions #FE Encore, the upcoming Pokemon Mystery Dungeon: Red Rescue Team DX, and Xenoblade Chronicles: Definitive Edition.
Nintendo in an e-mail sent by Nintendo the publisher said they would be announcing new Nintendo Switch games throughout the year. Major releases for holiday 2020 have not been announced yet, so it is likely we will see those games announced soon.
"You can look forward to announcements throughout the year, so keep your eyes peeled for more games joining this list!," reads the e-mail from Nintendo.