Presumably this will continue into the foreseeable future.
The Nintendo Switch has completely taken over the Japanese market, where no other console has been able to keep up. In fact, in the last twelve months, the Switch has been the top selling console in Japan every single month, based on Famitsu data; this is in spite of high profile PS4 exclusive launches such as God of War and Spider-Man, as well as major third party releases like Kingdom Hearts 3 and Resident Evil 2 in that period.
This aligns with the Switch’s performance life to date in Japan, which sees it within touching distance of the PS4 in the region (even though the PS4 has a three year head start on the Switch). The Switch’s success has been predicated on Nintendo’s hits-driven strategy, propelled by recent games such as Super Smash Bros. Ultimate and Pokemon Let’s Go, alongside continued sales and success of their evergreen titles such as The Legend of Zelda: Breath of the Wild, Mario Kart 8 Deluxe, Splatoon 2, and Super Mario Odyssey.
Given how ridiculously stacked this year’s lineup is for the Switch, we can see it continuing to dominate the hardware charts for the foreseeable future, not just in Japan, but also the rest of the world.