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

Nintendo revealed its Consolidated Results for the Nine Months Ended December 2015 and 2016 report which revealed that the Pokémon franchise significantly helped Nintendo's fiscal results. From November 18th, 2016 to December 31st, 2016, Pokémon Sun and Moon sold a combined 14.69 million units worldwide.

Consolidated Operating Results

During the nine months ended December 31, 2016, the worldwide release of Pokémon Sun and Pokémon Moon generated buzz and led to blockbuster sales of 14.69 million units. In addition, Super Mario Maker for Nintendo 3DS surpassed the million-seller mark. The release of the smart device application Pokémon GO led to increased sales of software in the Pokémon series released in the past and drove Nintendo 3DS family hardware sales growth, particularly outside of Japan. The worldwide sales volume for Nintendo 3DS hardware this period was 6.45 million units (10% increase on a year-on-year basis), while Nintendo 3DS software sales were 46.78 million units (20% increase on a year-on-year basis).

Source: https://www.nintendo.co.jp/ir/pdf/2017/170131e.pdf