Will households only have one NS or will there be multiple NS?

[Nuvendil]

First, don't look for the 3DS to die too soon. The Switch will be too expensive and frankly too bulky to replace it immediately. Nintendo's gonna ride that Pokemania wave as far as it will go, at least until the release of Dragon Quest XI and probably until the Switch can reach a lower price point. They know they can't go directly at the handheld audience with a device at around $300.   Which is one of many reasons they are currently hammering on the home console front.

Second, I would be more interested in multiple docks. So if you have a few TVs, you could hook a dock to each and move the console between them.