A new mobile Pokémon game could be on its way. The Pokémon careers site has posted a job listing for a "Principle Game Designer," saying that the individual will work with a team "to create an upcoming mobile game."
Another reference to mobile gaming is in the qualifications of the individual. One is "experience in mobile/video game design." Based on all this, it's not a matter of if a new Pokémon game for phones is coming, but when. Currently, the most popular mobile Pokémon title is Pokémon GO. According to GO's Google Play page, the game has been downloaded "over 850 millions times." Compare to other Pokémon mobile games in Play. Pokémon Duel has been downloaded over 34 million times, and Pokémon Quest has been installed over 5 million times. These are reasonable numbers, but pale to GO's numbers. Overall, the mobile market is strong for the franchise.
With Pokémon continuing to stay in the general public's eye, it makes sense to work on a new mobile title. This year sees the release of a core Pokémon RPG. While the next big game is always a huge deal, it also helps that this time instead of a small console, it's releasing on Nintendo Switch. Also, in May, the Detective Pikachu film will be released in theaters. This isn't a limited release either; Pokémon is going mainstream on the big screen. (There's even a rumor that a Pokémon Red and Blue movie is being considered for release after Detective Pikachu.) In some ways, Pokémon has become the most well known video game franchise.
While Pokémon GO has many regions to introduce, it's a good idea to release another mobile title to accompany it. The real question is, what could this game offer? GO offers players the ability to catch all sorts of Pokémon, and now you can battle other people in real time. Duel and Quest offer drastically different gameplay styles, so it's hard to think what a new mobile game will bring to the table. It could offer the most traditional Pokémon experience yet, but that doesn't sound probable because the company likely wants to drive sales to the core RPG on Switch. For now, it's all theories. We'll have to wait for the official announcement to get an idea of what to expect.