Recent Nintendo financials indicate the game is a ways off.
Remember the “core RPG” Pokemon title that Nintendo confirmed would be coming to the Switch? In a recent release (unearthed by NeoGAF), the company provided release windows for several of its upcoming titles including Pokemon. Long story short, Pokemon on the Switch will be releasing in “2018 or later”.
Other noteworthy titles in that release includes Xenoblade Chronicles 2 on track for its Holiday 2017 release date. Fire Emblem, Yoshi and Kirby for Switch have been slated for release in 2018. Metroid Prime 4, meanwhile, has “TBA” next to its release window.
As for the Pokemon title, it’s likely not going to be a port of Pokemon Sun and Moon like the rumours stated. Nintendo noted it to be a “core” title so we’ll likely be getting our first full-fledged Pokemon RPG on consoles in a while.
Meanwhile, Nintendo released sales figures for the Switch and its various games, which you can read more of here. The console sold nearly 5 million units since release while The Legend of Zelda: Breath of the Wild nearly hit 4 million units sold.