Honestly, a family of consoles isn't exactly gonna work. The Wii U and 3DS suffered from serious droughts, and having the same games for this supposed family of consoles is more complex than it sounds and definitely alienating for third-parties and just not worth it.
I remain on my stance about a handheld that can connect to TV. It's not particularly tough for something like the Tegra X1 to surpass the Wii U's processor, and it's much more modern than the PowerPC, thus easier to develop for. And it would be a real single plataform for them to focus their games on, they can market it as a full on handheld, it doesn't need to compete directly against PC/PS4/XB1, it doesn't need to be that close in power to them, either; merely being the secondary console of choice will yield more sales than a direct competitor.
Tl;dr handheld console, can connect to TV, good price point, single Nintendo plataform, using modern tech and slightly more powerful than Wii U. I can see this selling like hotcakes, really. Especially if it doesn't have any more gimmicks other than motion controls and touchscreen.