At this rate, it might even reach close to the first year sales of Wii U, PS4 and Vita combined
You are way too pessimistic, it'll sell several 100k a week when holiday comes. It'll destroy PS4+Vita+WiiU easily.
Anywho, Switch numbers are very cool to see, Nintendo have definitely improved their stock situation, and demand is still keeping up with supply. Good hold from DQXI, and I'm especially surprised by the PS4 version given the installbase. Might even reach 2 million lifetime including digital. Splatoon 2 is also doing amazing. Its attach rate is already ridiculous and climbing, without even factoring digital. Last but not least, the PS4 is also showing very healthy hardware numbers.
Overall, Japan, while it has faltered from its heights, is still a gigantic gaming market.