I think the tough thing is people maybe just don't want multiple consoles.
The Nintendo console has been in decline for a while if we look past the Wii, which seems more like a one-time craze (a well executed one) that can't be repeated easily.
Super NES - 49 million
N64 - 33 million
GCN - 22 million
Wii U - 17-18 million (currently on pace for)
It's a gargantuan task I think to convince people they need two video game boxes under their TV unless you have a killer, killer idea that changes everything about gaming like the Wiimote.