For myself, I think all the indications we have right now point towards a handheld and a console with either an entirely shared library, or a libraries that are mostly shared with a few exceptions. I lean towards the former because that would be just much simpler for customers.
I think Nintendo know that they will not be able to get broad (ie similar to PS4 and Xbox) support from the majority of Western publishers. Bethesda, EA, Activision, Ubisoft, WB, and their ilk will not support any Nintendo platforms to the same extent as they support Playstation, Xbox and PC unless Nintendo are somehow able to command a massive market share. They may give them a degree of support with titles that they think are particularly suitable to Nintendo platforms (skylanders, just dance, call of duty) but not much beyond that until there is a proven sizeable audience who are interested in more than just Nintendo games. Even if Nintendo achieve a decent install base, proving to these publishers that the revenue they generate will be worth the cost of supporting Nintendo platforms will need to be proven in practice before Nintendo can rely on it.
Nintendo have their sights set of different kinds of games.
Their own output from both their internal teams and external games they publish is always going to be their core offering, and it's what is making them the most money on 3DS, and any success the Wii U achieved is primarily down to that. If they could produce it more quickly, and increase the amount of sales per game, they would certainly improve their profits.
Indie devs are easy money for Nintendo. Right now there are technical barriers to publishing indie games on Wii U, and often insurmountable technical barriers to publishing indie games on 3DS. If they can provide a home console and a handheld console that the majority of indie devs are able to access with relatively low difficulty to publish on, Nintendo can make their 30% on far more games, and fill up the gaps in their release schedule much more easily.
The Japanese mid-tier publishers are in an uncertain position. Just looking at the TGS announcements from Sony recently. A lot of publishers are unwilling to leap head first into the next generation of home consoles. The majority of games recently announced for PS4 also have either a PS3 or PS Vita version also in the pipeline. The PS4 has sold OK in Japan, but it's clear that the PS4 is not offering an install base enough to carry a lot of games. At least not yet. The audience for handheld games is much higher proportionately in Japan than either North America or Europe. If Nintendo can provide a platform where for less work than it takes to shift a PS4 & Vita version, devs can ship a game for a handheld console that is market leader in Japan, and a home and handheld console in the rest of the world, they will be an attractive proposition for a lot of games. The effort to ship a game for both PS Vita and PS4 is nontrivial. If Nintendo can offer a similar set of platforms, with greater harmony between the two equivalent devices, I believe a decent selection of publishers in this category could find a viable opportunity in supporting Nintendo platforms.
Whist a lot of mobile/tablet games are pretty specifically suited to these platforms, there's obviously some that make sense to carry over to dedicated gaming platforms. We've already seen instances of this on Nintendo's current hardware. If they can offer a platform that has great support for simple ports of mobile games, both in terms of underlying tech and interface, they will be able to cherry pick from the best of mobile, and expose an entirely different userbase to already proven games.
Nintendo also really need to get their house in order with regards to the virtual console. It was a groundbreaking initiative when it first launched, but it needs to evolve. Nintendo have an unparalleled heritage when it comes to back catalogue, they should be aggressively leveraging it in all their platforms. Establishing next generation version of virtual console would be an excellent differentiator for their platforms, and it would be a decent earner. Nintendo's virtual console should offer me games that follow me to every single future Nintendo platform for the foreseeable future, offer cloud saves between devices and run at least as well as it did on the original platform. They should offer an extensive library chronicling as much of Nintendo's recent and not so recent history as feasible, with meaningful contributions from anyone else applicable. They should also provide some kind of service along the lines of PS+, where in exchange for a reasonable monthly fee, I get a selection of classics from Nintendo's back catalogue, and interesting recent games from outside Nintendo.
Efforts towards building bridges with large western publishers is not a waste of time, but any discussions or negotiations they engage in go far better if Nintendo get new platforms of the ground and into consumers hands better than they have with their current platforms.
So what does this mean? It means shipping hardware that Nintendo have a toolset designed to streamline their development process for, and are able to ship a game once that owners of any NX device can play. It means getting robust support of the most widely used engines, unity, unreal, game maker and more, across both their handheld and home console, and both their handheld and home console to have the horsepower to be able to reach something approaching parity (for their given resolutions), and not require a massive amount of optimisation to support. It also means enhancing the online side of their operation, offering more robust account systems, having devices and infrastructure that make online interactions simpler and faster, and keeping people engaged more in online interactions within their software and within their broader ecosystem.
I think each of these are inside Nintendo's capability, and I think in some way they know that these are their best opportunities, it's probably just going to be a question of execution.
Any kind of backwards compatibility is up in the air. Exactly what kind of horsepower they will aim for is tough to second guess. Trying to predict form factor, controller design, and hardware configuration is all the route to madness, but Nintendo have proven themselves more than capable of both delighting and infuriating in these areas.
I look forward to hearing more about NX, but one thing I know for sure is that betting against Nintendo is a fool's game.