Eh, the 3DS vs. Vita gap will be about 55m while the PS4-WiiU gap will be 80m+

well, since you brought it up ... I humbly disagree with the idea of ​​adding number of "Gameboy Color" in the total number of gameboys, for a very simple reason ... 

Old Gameboy, before the color> Hardware Review, better display, lower power consumption, lighter and smaller console, etc ... a lot of changes that did not create the classic division between "old generation and new generation", ie all games running on all versions of the console. (Or, at least, the overwhelming majority, something crushing, like, 2-3 games only work with a specific version.) 

Gameboy color> consider the gameboy color a new generation and a different product, because there are several games that only worked on the gameboy color. Yes, there were games made for gameboy color / gameboy Old, but begins from the moment that the gameboy color gained "significant number of exclusive for gameboy color" and the idea "my old gameboy can not run it, I need to buy the new Gameboy Color to play this exclusive game for gameboy color! "at this point there was a break and sales gameboyXGameboy color should be treated separately. 

This is my humble opinion, you can agree or not.

You want to guess what my little niece asked for Christmas last year? Hint: it wasn't a Nintendo handheld. 

And only 20m people bought a Gamecube just to play Nintendo games. That should tell you all you need to know about the core Nintendo audience. It isn't very large. 

I'm projecting

3DS - 72 million LTD
Wii U - 19 million LTD

PS4 - 100 million LTD
Vita - 13 million LTD

The worrying thing about the 3DS is the yearly shipments last year and this year ... they are the lowest Nintendo has ever had for a handheld since the introduction of the GBC and Pokemon around 1997/98.

Last year was about 12 million even with Pokemon X/Y, 2DS, Animal Crossing, Luigi's Mansion, Monster Hunter 4 for Japan, etc.

The smartphone/tablet effect is real, it's like a cancer that's just continuing to spread and choke the life our of the handheld business.

The other issue is when mommy/daddy buy that shiny new iPhone 6 ... guess who gets the iPhone 5 ... usually it gets passed down to the kids. So they are getting introduced to these devices very early. Or tablets, mom/dad wants that new iPad mini, so they give the kids their older iPad. That's a big problem too.

Mario and Pikachu still have sway, but against this foe, they're simply not enough. 

The PS4 - Wii U gap will be bigger.

I don't think the smartphone is going anywhere, neither is gaming on smartphones. The PC was always a really difficult platform for gaming. I grew up with a PC in the 90s, and installing a game and sometimes getting it to run properly could be a nightmare, I think PC gaming never took off among the casual masses for that reason. 

But beyond that, the PC is kinda firmly stuck in the bedroom/den/work room ... the smartphone can go anywhere and is far more convienant in that sense. 

Angry Birds will fizzle out sure ... but then it will be replaced by some other new smartphone craze whether it's Candy Crush or whatever. That's part of the appeal of iOS/Android is there's constantly new games to try so that makes their ecosystem feel so vibrant and alive ... even if the game sucks ... so what, it's not like you paid $40 for it. 

It is like a cancer to handheld gaming IMO, every year we've seen the number of portables decline. This year will be less than last year. Next year will probably be even worse. 

Well smartphone gaming really only starting to pick up steam around 2009 or so, the App Store wasn't even open until a few years after the iPhone came out. Angry Birds is the first bonafied smartphone blockbuster and that launched in December 2009. 

Naturally portable handheld have taken the brunt of the damage and the casual audience of the Wii has been gobbled up first by smartphones. 

Unfortunately these are two areas that happen to impact Nintendo most directly, but Sony obviously took a huge hit too as their handheld business has basically been all but wiped out (good luck convincing a teenager/adult to carry a Vita in addition to a smartphone). 

PS4/X1 are probably the least impacted, as they serve the furthest market away from smartphone games, but I think even there we will see a general decline in dedicated home console sales this gen too. PS4 is not going to match the PS2 and X1 is going to be well below the X360, so that section of the market isn't growing either. It just hasn't taken the same hit. 

PS4>WiiU gap for sure imo
PS4- 100m (minimum)
WiiU- 30m (maximum)
Gap- 70m (at least)

3DS- 80m (maximum)
Vita- 10m (minimum)
Gap- 70m (at best)