You aren't factoring in people who own neither a 3DS or Wii U that may buy at least one NX sku.

Lets use the 2015 releases as an example, lets say someone wanted to play Monster Hunter 4, Majora's Mask 3D & Happy Home Designer but those 3 games weren't enough for them to buy a 3DS, lets say they are also interested in Splatoon, Super Mario Maker & Xenoblade X but again those 3 games aren't enough to buy a Wii U. Would that person be more likely to purchase a single device that plays all 6 of those games?

Another factor that you aren't considering is the increase of software sales, certain games have been hindered by the fact they are stuck on a platform with a small userbase. Splatoon & Mario Maker are big successes and will each sell 5+ million but what if they had the entire 3DS audience to sell to as well? These games could very well sell over 10 million.

A third major factor is that Nintendo can diversify their lineup by not having to make 2 separate entries of many franchises. Instead of releasing a Mario Kart title for the handheld then 3 years later another Mario Kart for the console, they can release one and support it with DLC then release a new IP 3 years later. This potentially leads to more Splatoon-like scenarios of new, exciting franchise being created which increases the devices appeal.

Agreed. 

Here is DS vs 3DS. And just keep in mind that you had healthy PSP sales last gen as well (which did better than 3DS) where as this gen you've just had 3DS performing the best with PSV dead. 

I remember a few years back when people were calling me, rocketpig and kowenicki and some others ridiculous when we said that the handheld market would be eaten by mobile and convenience gaming. Well; here we are. Hard to explain that decline, especially when you tally in the atrocious Vita sales on top of this.

In fact here is my estimate when you include PSP and PS Vita.

Ouch, that's a disaster, in relative terms at least. I wonder what the future holds, I've also maintained that the 3DS would be the last dedicated handheld console, that one's still up in the air but it seems likely as ever.

That's why I've kept this post bookmarked: http://gamrconnect.vgchartz.com/post.php?id=3961947

Less than 20 days left for Super Mario or Mario Kart to release on smartphones. It's not going to happen. Likewise, the 3DS won't be the last dedicated handheld console. I mean, come on. The 3DS has been the best selling dedicated gaming hardware in Japan by far, so it's preposterous to suggest that there won't be another handheld.

So the people who called you guys ridiculous for your predictions were right to do so.

I have no idea at one point you would consider there to be a difference between "handheld" and "dedicated handheld". The 3DS already has an internet browser, cameras, movie and music applications. So you are thinking of something like a phone?

kowenicki's predictions were that Nintendo would not make another handheld and instead move their games over to smartphones; that is definitely wrong. I have no recollection of what exactly rocketpig predicted.

There's a notable difference between predicting a decline* and the end of dedicated handheld consoles. Like I said, I don't know your definition. But if the main purpose of a device is to play video games, then it is a dedicated gaming machine. And that's pretty much guaranteed for NX. If you want to feel good about correctly predicting a decline, fine. But you won't be right about the other part which was a much more daring prediction and the one kowenicki and others were ridiculed for.

*A decline was likely to begin with, because Sony had to come up with an answer to the collapsed PSP software market outside of Japan; and the lack of such an answer would have meant that Nintendo would have had to make up for Sony's losses in hardware sales in addition to selling as many units as the DS. The common assumption was that Sony would fail to come up with something.