Well, we knew it would be SOMETIME in the 2020s...
http://www.nintendoworldreport.com/news/51930/brain-age-for-switch-launching-3-january-2020-in-europe
Dr. Kawashima's next stop in Europe will be very early in the new year.
Nintendo of Europe have confirmed a 3 January release for the training game on Switch, a mere week's turnaround from the game's Japanese release. The stylus announced with the Japanese release will be included with retail copies of the game as well.
As of press time, a North American date has not been confirmed.