I think it would have sold more, as the Vita wouls die and all devs who wanted a premium market to sell their games in handheld would only have one option.  So the few strong Vita IPs would likely migrate there in time.  And Nintendo's market is 1000% better than 3DS and Wii U. 

Smartphone competition is really not the issue people think it is.  The damage it was going to do has mostly been done, scooping up people who never were all in on the dedicated gaming hardware thing, it's just that was the only option.  And 95% of those people were the new consumers of Gen 7.  If you want a handheld-style gaming experience, phones are a pretty miserable choice.  Few devs pushing the hardware, most who are are just poor man's versions of console games (Modern Combat, Asphalt, N.O.V.A, etc), freemium model overrunning the market to the point kf toxicity and to the extreme detriment of game design, overly simplistic gameplay, lack oh physical inputs.  Seriously, it's a shoddy substitute.  It's a competitor on paper, but the handheld and mobile market are radically different in practice.

I don't know if it would habe hit the over 90 mil mark.  As for kids growing up more mobile than handheld, I think what you are really seeing is more kids growing up playing on the go in general.  Hundreds of millions of people young and old game on mobile that never ever would have touched a handheld.  As a result, yeah, of course they outnumber handheld owners.  But they were never going to buy one to begin with.  How many sales were actually *taken* and how many are sales to entirely new customers.  It's hard to quantify.  

Also, I think Nintendo, with the right marketing, could have instrumented some countermeasures against the mobile gaming market with children.  I mean, mobile games are some of the most nakedly psychologically manipulative products on the market and I sure as hell wouldn't let my kid play most mobile games.  It would have been work, but I think it could be done.  And I definitely think they could have picked up some more adults as well.

The Switch is still I think a superior solution, mainly because I think it allows them to do things handhelds could not.  But I think handhelds could have held their ground.

Those wanting a "premium" portable gaming experience beyond what phones offer are a hardcore minority though. I mean, us enthusiast gamers can talk all day about how crap phone games are, but the average consumers has low standards and is easily pleased. Where once parents bought their kids a Gameboy or DS, now they just get them a cheap tablet.

In the end though, I think the proof is in the pudding, that we'll likely never again see a mainstream device built just for portable gaming. (Excluding a possible 2DS-style Switchless Switch, which, if it gets made at all, would sell only a fraction of the hybrid model)

You're not getting what I am getting at: that 80 to 110 million is and always was that hardcore minority.  Handhelds have been mostly for hobbyist gamers for pretty much their entire existence.  The majority of the more flippant casual market that now games on phones were never interested in handhelds in the first place because it's not just putting it under your tv, you have to carry it around.  Until Gen 7 I don't think the majority of that market was casual, not even remltely close.  But of all the people who wanted gaming on the go, yes, handhelds have always, from the beginning, appealed to a minority as we now know.  The majority just never had a product for them and now they do.

And just because Nintendo stopped making them doesn't prove anything.  AAA devs stopped making horror games and claimed that the lack of them on the market proved they were dead when surprise surprise there was demand.  Difference here is that Nintendo is the undisputed handheld heavyweight champ and there's no one out there who can take up the torch.  And the Switch would pose a significant challenge. But if, say, Sony made the Switch and Nintendo made the next handheld, it would have been a fight but I very firmly believe they would habe had success.

The mobile and handheld markets appeal to very different demographics, now more than ever.

If there was a future for pure portables, companies would be making them, but there just isn't any need for them any more, between them phones and Switch have the audience portables once served covered. 

Well there hasn't even been enough time to examine a post-Switch market, but companies didn't make handhelds much because every company that tried got systematically eviscerated by Nintendo.  The Game Gear, Lynx, Wonder Swan, NeoGeo Pocket Color, the N-Gage, now the Vita.   The only successful competitor to Nintendo in handhelds was the PSP, but even then the DS sold almost 70 mil more.  Companies just gave up because handheld gaming was basically a monopoly under Nintendo.   

Will there be new ones in the future?  No, because even at a cap of 90 to 120 million sales, dedicated handhelds are still a minority at their best and Nintendo can hold on to a very large part of that with the Switch.  

I'm just saying the demand did not go away.  Nintendo just moved on and no one is there to take their place and also they still habe a foot in that camp.