Nintendo revealed its Nintendo's Consolidated Results for the Years Ended March 31, 2017 and 2018 report which indicted that Pokémon Ultra Sun and Pokémon Ultra Moon sold 7.51 million units or just about 50% less of what Pokémon Sun and Pokémon Moon sold last year in a shorter time span.

Operating Results and Financial Positions for the Fiscal Year Ended March 31, 2018

Nintendo 3DS hardware sales remained solid in each region even after the launch of Nintendo Switch, with sales during this fiscal year reaching 6.40 million units. For the Nintendo 3DS software, Pokémon Ultra Sun and Pokémon Ultra Moon sold 7.51 million units, while overall sales for this fiscal year totaled 35.64 million units.

Source: https://www.nintendo.co.jp/ir/pdf/2018/180426e.pdf

Pokémon RPG for Nintendo Switch Still Scheduled for Release in "2018 or later"

Nintendo also revealed in the Earnings Release for Fiscal Year Ended March 2018 - Supplementary Information in the Launch Schedule of Primary Nintendo Products by Region (extracts: Apr. 2018〜) section that a Pokémon RPG for Nintendo Switch (temp.) is still scheduled for release in "2018 or later".

Source: https://www.nintendo.co.jp/ir/pdf/2018/180426_4e.pdf