On June 26th, 2017, Nintendo announced their Earnings Release: Three Months Ended June 30, 2017. The Nintendo Switch is selling faster than Nintendo can produce the system and has sold 4.7 million units. The Nintendo Co., Ltd. Earnings Release for the Three-Month Period Ended June 2017 - Supplementary Information indicated that the previously announced Pokémon RPG for Nintendo Switch will be released in "2018 or later". With the development of a new game engine for Switch, it could take longer to develop and the game might not be released until 2019.

Source: https://www.nintendo.co.jp/ir/pdf/2017/170726_2e.pdf