We need to get this third pillar talk out of here. It's pretty clear that NX is going to be Nintendo's single ecosystem going forth, and that in itself will be a single pillar.
Other pillars will include their mobile games, theme park ventures, movies, tv shows, etc.
So NX is their future for dedicated gaming devices. It's not a device itself, and it by itself is not a successor to Wii U or 3DS, rather, it's a platform which will encompass multiple devices, possibly more than two.
So get outta here with that third pillar nonsense.
Edit:
Also Kimi never mentioned the phrase "third pillar." Nintendo has been shockingly clear and consistent on its messaging for NX (being an ecosystem/developing environment/platform) so I don't know where all this "doublespeak" is coming form.