The way I see it, there's no way that Nintendo will let you buy a handheld game and then let you run it on a tv as well without paying an extra fee.
It would be replacing their future home console income. Nintendo will be planning on having a beefed up version of their system that is purely for home tv use, that uses this new OS.
Not only that but each handheld game would have to be optimised to be able to run at tv resolutions of 720 or 1080. Effectively meaning that every game would have to have extra work put into it, without any extra money coming in to cover it. And many people playing the handheld version will never play those games plugged into a tv. So basically extra work put in for less money and not guaranteed to be used by everyone.
A more Nintendo way of doing it would be to sell the handheld version of the game, then also offer a download for $10 or so, that allows that particular game to run on the tv.
Nintendo is super good at squeezing extra money out of people and I don't see how this fantasy of a console-powerful handheld that replaces an entire revenue stream fits into that. As per usual before a Nintendo launch, there's a lot of wishful thinking going on before the eventual crash and depression caused by the actual reveal of what they've really made. Which is a shame because it causes most people to just get upset about the specs of the thing rather than get excited about the gameplay made possible by the weird and inventive hardware they come out with.
What I would do here is to have the NX as a unified console, but sell it in 2 different packages.
· Portable-only: A cheaper package, containing the tablet screen/controller and the detachable controls. It would also feature its own cartridge port, so it is capable of executing the games, obviously.
· Desktop experience: Contains all of the above, plus a charging dock for the controller and an extra box that connects to the TV and has its own bigger CPU and GPU, and also its own cartridges slot.
This way, you can have a handheld device that works as a standalone handheld and is a fully portable console on its own, and also a, let's say, PC-like box connected to the TV that will be capable of displaying the handheld games on the TV with better resolution and framerate. On the other hand, the TV box, with its own cartridge slot, would receive its own line of games that require more power to be executed, hence becoming the de facto home console of Nintendo.
This way Nintendo would have a unified platform, but 2 lines of products: the handheld-only games that could also be seen on a TV screen for the audience that's not interested on desktop gaming; and bigger, more resource-needy games that could only be played in the more powerful TV box.