Atlus Co., Ltd. (株式会社アトラス, Atlus Corporation) is a subsidiary of Sega that is best known for developing the Megami Tensei, Persona, Etrian Odyssey, and Trauma Center series. No, they won't bring Persona 5 to the Switch.
Joker, the main protagonist of Persona 5, was announced as the first DLC newcomer for Ultimate at The Game Awards 2018. He was later added in, along with Mementos, multiple spirits, and multiple music tracks on April 17th, 2019. Tsubasa Oribe from the Fire Emblem crossover title Tokyo Mirage Sessions ♯FE also appears a Spirit, which can be enhanced into her Carnage form.