Vita will have a good launch but wouldn't be surprised if it saw a fast drop in sales like the 3DS, which went from like 3.6 million in the first quarter of sales to 710k in the second quarter. Nintendo had to back off the 16 million forecast.
You knew even the launch sales didn't meet expectations when there were all kinds of promotions available along with inventory.
I'm sure both 3DS and Vita will reach tens of millions in accumulated sales in several years. But consider that Apple sold 20 million iPhones in the most recent quarter, for a design which is a year old. And then you have tens of millions of other smart phones being sold as well. And soon tens of millions of tablets sold each quarter.
So where does a $250 dedicated gaming device fit in? For people who buy smart phones and tablets every 2 years, that $250 gaming device has to offer something really unique. Games like Uncharted are nice but will it sell systems when you can have a better Uncharted experience on the tens of millions of PS3s already out there?
Good luck carrying your PS3 around with you mate ;-) Along with your big HDTV and portable power generator to power it all.
On a more serious note, i find a major flaw with this logic. You say that the Vita has no market unless it can do something phones can't. You mention the very thing that it can do that phones never will (i.e. big budget portable games that no-one will invest in developing for iPhone or Andriod to sell for $0.99), and then dismiss it because home consoles exist, thus failing to acknowledge the "portable" point of a dedicated "portable console".
PSP sold 70 million. DS sold 146+ million. Yes iphone is big now, and 3DS has been a slow burn, but lets wait and see when Vita is released & 3DS actually has games (and now it's at a reasonable price) before deciding for everyone how many people want or don't want the deeper portable gaming experiences that these consoles are made for.
I find it utterly amazing how many people now-a-days parrot the same line about "i don't play portable games on the go, and so 3DS & Vita are doomed", when they simply fail to see that the rest of the population of the world =/= them.
I have an iPad, i have a PSP. I commute for at least 1.5 hours each day to work. I game on my journey on my PSP. I barely use my iPad for games because there's nothing on the appstore that can hold my interest for more than 2 mins. Vita is a massive upgrade for the PSP and i see it as exactly what i need. Any argument over it's size is moot, when on the same hand you're arguing that the Vita is made redundant by the flaming iPad or any other such hulking big tablet device (I'm yet to see a man fit an iPad in his pocket. That's right... we carry bags). And any argument over console-like games on the go I consider rediculous, because there's lots of potential and demand for these kinds of games, and the hundreds of millions of them sold on PSP and DS only validate that fact.
What i feel many fall to realise is that these deeper games would be economically impossible on iOS without being able to port to other more high margin platforms. If psp and nintendo handhelds dissappeared, then it wouldn't suddenly make iOS and android with their $0.99 appstores any less of an economical risk for pubs and devs. In fact the converse would be true.
I see iOS and android not as direct competition to the 3DS and Vita. I agree that there is some overlap. However i think these platforms are merely seeing success as gaming platforms because they've been effective in capturing a market that previously occupied itself with the crappy mob phone games like "snake" on older phones. i.e. the mainstream consumer who was never in the market for a gaming portable in the first place. Such consumers never owned a DS or PSP, and so aren't at all potential consumers of Sony and Nintendo that have been snatched away. The folks who bought DS' and PSP will still appreciate the kind of gaming experiences that they identify with those platforms, and in that sense iOS and android will never compete. It's like arguing that the Wii was stealing away the Xbx360's consumers... it wasn't... they were a entirely separate market.