I am going to enter this "will the Vita be around in 2017" argument from a different perspective and say that while the answer will be yes, that will be due not to its success, but to the failures of both efforts to move the audience to the PS4, and the fact that the actual NX is imo unlikely to bear the slightest resemblance to the actual product discussed in these threads, which is delusional vaporware on par with a Peter Monyleux game.
In the former case, I think Sony is actively trying to kill the Vita, but I suspect they will fail. There remains a solid audience for games exactly like Digimon Cybersleuth, Sword Art Online, God Eater, Tokyo Xanadu or Falcom's other titles that
1. Are the right technical mix for the Vita, didn't max out its power early on for budgetary reasons, and therefore have continued space to increase production values for some time
2. Sell in the 70K-150K very reliably
3. Have a sufficiently capped audience that it is unclear if they would neccisarily benifit sales-wise from the 3Ds
4. Whose audience has no real reason to go to the PS4
There is such an extreme conservatism among both the remaining parts of the Japanese audience, and Japanese developers outside the top tier, that I can easily see many being happy with the Vita for years much as they were with the PSP, and to Sony's fury.
(Warning, some of what follows is speculation, but so is virtually everything NX related, and I think cold water on the subject is in desperately short supply, especially from a more technical perspective)
The second reason for my belief in a Vita zombie-afterlife is that I do not buy the NX future. The NX that is being painted, a console/handheld hybrid at whose core is an original operating system that can easily scale up and down software without burdening developers, yet run almost all modern engines is technical vaporware coming from a Japanese company. Even Microsoft, which has some of the best engineers in the world, would struggle with such an ambitious concept, and frankly did to break into the market with Windows phone. Even Apple took years to get IOS to scale properly, and to have universal apps rather than IPAD/Phone versions.
Japanese companies, by contrast, have never been players in the OS market, and have basically been a decade or more behind the West in PC development for sometime. For whatever reason, Japanese firms seem to struggle with OS development and engines. See the struggle so many companies had with the Unreal engine last generation, and yes I know documentation was an issue, but still. Currently, Sony and Nintendo seem to struggle desperately to implement even basic functional features on their console OS. Nintendo is a generation or two behind on Virtual console support, and substantially so regarding where Western homebrew developers are, and imagining something like 360 backwards compatibility coming from Sony seems absurd when they seem to find PS2 classics such a struggle on PS4. Yes I am certain they will get there eventually, but the point is they seem to treating it as a struggle a tier or two more challenging, than say,I suspect Microsoft's engineers would find the same thing.
This all brings me back to the idea that everyone seems to assume that Nintendo can not only release hybrid hardware, but have its internal engineer somehow develop their own version of IOS or Android nearly from scratch, get it to achieve far more ambitious things on vastly more limited hardware, and yet somehow make programming and engine support so simple in terms of having the OS do everything for developers that ports should be as simple and easy as to be free. That whole thing seems implausible, and sounds like the sort of nonsense you would get in 1993 supporting the 3DO. It is what dreamers looking at the market think would be really successful, rather than what realists burned by experience of it think would actually be possible. And i think a lot of wistful speculation from Nintendo figures about where the long-term future of the market and hardware lies is being confused with concrete plans for technical features in a product coming out in the next twelve months.
This is not to say that i believe the NX will be a disaster. I do not, though I expect a substantial decline from the 3DS. Rather, I think the final product will be vastly less ambitious technically than the assumptions that a lot of people have been making, because to try and produce the product that has been built up in people's head by speculation would be to in fact court technical disaster. It will be a 4DS, albeit one in which Nintendo makes extensive efforts to make it more developer and mobile port friendly, but will still rest on first party output with a bias towards portable offerings, albeit with an evolution of their current trend of having those converge with their console counterparts(see Smash 3ds, Mario 3d land). That will likely be enough to overtake the PS4, perhaps several times over.
That said, I do not buy the idea that its very appearance will instantly transform the market, end the current generation,and thereby finish off the PS Ecosystem approach and the Vita along with it. The actual process will be slower, the challenges for developers, especially much smaller ones as opposed to the big boys like Square Enix and Capcom who have not been deterred by difficult environments, much greater. Hence, I see no reason why the Vita software line-up which has found a profitable home on the console, is likely to max out budgets before maxing out system resources, and has already been burned by a PS4 porting campaign which is Sony subsidized will suddenly rush to abandon where they are comfortable for an unknown market on an unproven system where they have no preexisting audience. SE is enthusiastic about NX for the same reason they have been desperately trying to prop up the PS4; they need it to succeed because they are a company that has historically cared a lot about production values and its success would solve a lot of problems for them. But extrapolating that desire into either the highly niche lower tiers of the Japanese developing community, or into concrete results, seems premature. SE may pray for the PS4 and NX to be successful and finish off the Vita, but in the last year it is the Vita which has seen the greatest increase in their support.
