Master analyst, Michael Pachter, predicts that Switch will not sell near Wii.

[Zippy6]

Kakadu18 said:

Why do so many people think every Nintendo console only has a life span of 5 years?

n64 - 1996 (5 years)
GC - 2001 (5 years)
Wii - 2006 (6 years)
WiiU - 2012 (5 years)
Switch - 2017

This is probably why.

But boiling it down to "must sell X for 5 years" is a very dumb way of looking at it.