I thought it was stupid + waifus that did it for Japan

I don't think 1-2-Switch has the latter

its doable since Switch is also a portable.

and 3DS sold better than DS in its first year despite a higher price tag and mobile having grown significantly between 2004 & 2011.

If the hype is real with Splatoon 2 in Japan, then I can see it happening. Dragon Quest XI (a title I think a lot of people kind of forget about) should also help in pushing Switch sales over there even though it's multiplat since every new entry sells around 4-5m in Japan alone.

Definitely possible, handhelds are Japan's largest gaming hardware market. Japan makes up the highest portion of 3DS sales with well over 20 million sold there.

I think that demand will be high, so it could possibly hit that mark. Now, the problem is if Nintendo is capable of manufacturing a huge ammount of Switch.

In Japan alone? No.

3DS sales are a pretty even split among the three major regions. According to Nintendo's latest shipment numbers they are

Japan-23.13 million

Americas-21.96 million

Other-20.21 million

4 million may be pushing it, i think over 3 million though is very likely.

Agreed, iPhone and Android have simply pushed too far into the mobile space for dedicated handhelds to be massively successful any more. Combo that with pricing that is effectively higher than PS4/Xbox One, and it's looking like another WiiU to me.

Nintendo is in a tough spot with the thing, because 3DS is still selling, the only handheld to do much of anything, so they're effectively competing against themselves despite the 'unified' production idea.

This all could have been fixed with a dedicated handheld version for $199 or so, 4" screen with non-removable controller integration and no included dock.

In fact, two SKUs would have been probably far more successful than the gimmicky thing they're putting out.

Model 1 : The 4" dedicated handheld listed above : $199.

Model 2 : A dedicated home model, no screen or mobile aspect whatsoever : $149

Play the exact same games, unify their development/etc, but with models specific to purpose instead of the expensive, chunky not-quite-convenient thing they've come up with. Hugely less expensive to the consumer, and for the superfans like those that have both 3DS and WiiU, those people would probably buy both models anyway.

The decision to go with touchscreen probably makes this impossible now though, even as a later SKU growth. At best a smaller handheld variant may come out, but an affordable screenless home model for people who don't care about traveling with it at all is out of the question.

I hate touchscreen gaming, so I don't bother with phone/tablet games either, but those that don't mind it mostly play iOS/Android anyway.

Even withiout the awful accessory pricing, $299 is going to really stunt this thing out of the gate IMHO, once the superfans get through with the first shipment. It reminds me a lot of the XB1 annoucnement and plans, where they clearly expected to be the dominant console of the gen, thought that forcing Kinect and $499 USD was all just great. And sure enough, the hardcore Xbox fans almost universally agreed with all of that (check the forums back then, it was as you'd expect : XB fans saying 'yay, this is just fine', and literally everyone else saying 'wtf, really?'). The XB1 initial plans seemed to have been developed in an echo-chamber of yes-men with no critical big-picture analysis, and it really seems to me this NS launch plan is yet another thing that probably sounds great to many of the supercore Nintendo fans, but doesn't light up the regular consumer at all. As seen by the Dreamcast and WiiU, aiming square at your biggest fans is not a guarantee of success. And I really liked both of those systems (despite thinking the WiiU tablet was a mistake, and the pricing was terrible).

I'm sure all of that sounds incredibly harsh, but it's what I'm seeing. Despite all of that, I still think Nintendo has the best overall 1st party in the industry.