Nice, that you included other systems time to that milestone. I thought 3DS must have lost steam later on, but looking at the list I realize that 3DS is actually pretty strong in Japan, currently 3rd in total sales (only topped by Gameboy and naturally DS). There are five systems sitting between 5 and six million units in Japan (which Switch should beat this year): N64, Sega Saturn and the Vita. After that is a big gap with only the PS4 in it, which obviously is still a moving target. The next settled target is PS3 with just above 10 million units. Can Switch get there next year? Possible.
Hmmm... 16th spot for the Switch. But the N64 is only 500k in front, and 800k for both Saturn and Vita, so the Switch should overtake them before the end of the year.
After the Vita there's a big hole, next is the PS4 but that one's still selling (yeah I know, the Vita too, but just barely, following then is the PS3 at over 10M already, so that's gonna take a while longer. 10th spot is the Wii at 12.77M Will the Switch surpass it before the end of next year? Let's see...