For home use phones and tablets are replacing PCs so the average consumer's not going to have a device to use the service on... unless it also supports tablets and phones but then they have to severely compromise the specs to meet such a lowest common denominator. A console today is basically a pre-built gaming PC at a mass market price point. That's what the average consumer is going to be interested in. If the NX was a service Nintendo would still need some sort of base hardware SKU for those that don't want to figure out the hardware requirement themselves.
For obvious reasons I feel the console industry wants us to buy new consoles with less significant hardware updates more frequently. I don't like it, I won't support it, but my lone "vote" will mean jack ****. In a world where F2P scams and microtransactions are a sustainable business model I can see this approach being successful enough to become the new standard. The industry has clearly shifted over the last ten years to one that seeks to exploit their customers.
When I say NX is an OS, I'm talking both hardware and software. What I've always said is there will be:
A base handheld (that picture is the prototype)
A base console
A Rebranded Wii U
Powered by NXA Steam-like app that is has both iOS and Android base standards.
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That device, if legit gives the best of both worlds. Physical Buttons, click wheel buttons and force feedback touch. That would allow for scalable cross-development.
edit: example of how it might work from NeoGaf.