Yeah I am surprised by Nintendo's high expectations for the NSW going into its 6th fiscal year. However we have to keep in mind Nintendo's 1st fiscal year was about 1 month long compared to most consoles having 5 months.
This next fiscal year will be quite interesting, because I am curious about which markets will do the heavy lifting.
javi is using the PS4's fifth full fiscal year against Switch's sixth full fiscal year, so there's no benefit given to Switch for its one-month fiscal year zero (let's call it that way for simplicity) vs. the PS4's five-month fiscal year zero. So in the comparison that is being used here, it's Switch which is the older console. For the DS he used the sixth full fiscal year, so in that comparison the DS is the older console.
So when it comes to full fiscal years, the DS is in first in year 6 with ~18m units shipped, followed by the PS2 with ~16m in production shipments (Sony's reporting method differed as most regulars in sales discussions are probably aware of). The PS4 accomplished ~13.5m, by the way.
As for Switch's regional distribution of units in the recently started fiscal year, it's unlikely that any region specificially will stick out as doing the heavy lifting. All four major categories (Japan, Americas, Europe, Other) will continue to see steady sales, because there's nothing indicating otherwise. Japan may be the closest to the saturation point, but we aren't quite there yet; Switch's sales aren't eroding like they did for the 3DS which was far off from its peak when it entered year 6.