Going by when they launched next gen not by when they stopped supporting it.
NES 6 years 85-91
SNES 5 years 91-96 (tech was evolving way more rapidly in that period)
N64 5 years 96 to 2001
Gamecube 5 years 2001 to 2006
Wii 6 years 2006 to 2012
WiiU 5 years 2012-2017 (really 4.5, fall launch for WiiU, early spring launch for Switch)
So basically every Nintendo console has gotten about 5 years min, even the ones with weaker sales (GC and WiiU)
Only the 2 consoles that had dominating success(when WiiU launched Wii still had a massive lead over PS360, they had started narrowing the lead at that point, but it was really 2013-14 when PS360 were still selling great and Wii pretty much stopped that they pulled to a respectable distance) got 6 full years before a successor.
So that said, basically Shiggy is saying he see Switch possibly being a NES/Wii like success and thus would get 6 years maybe before a successor.
Nintendo has been remarkable consistent with this. Unlike MS which gave Xbox like 4 years, 360 like 8 years and now is releasing a console that is probably double the power of the XB1 4 years later (even though it is "same gen")
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut







