New Pokémon mobile game set to release by March 2020

A surprise announcement teases a new Pokémon mobile game. What could it be?

Without prior warning, it appears that another company, DeNA, has teamed up with The Pokémon Company to produce a mobile game based on the Pokémon license. According to a financial report made available by DeNA, it will be released before March 2020.

It is not known what the game will be, however. What do you think it will be?