I want to add too that 3DS went from 5'5M in 2012 to 5'0M in 2013 and you know what games came for 3DS that year in Japan?:
Edit: oh and Animal Crossing New Leaf..., that little and unsuccesful game....XD
Animal Crossing was 2012 in Japan.
The difference is that 3DS had a price cut in year 1 and a revision in year 2, Switch is entering year 3 with neither of those things meaning the trajectory will likely be different from 3DS.
Media Create sales 3DS
3DS sales started out really slow, the price was too high and the software output too low, but the price cut in summer followed by big games in the fall led to a record first year.
Momentum from late 2011 continued in 2012 and this is when the system started to get a really steady output of big games and a revision. This was the 3rd best year for any system ever in Japan.
2013 was another amazing year but it's extremely hard to top what 2012 had and it suffered a modest decline. And by the beginning of 2014, 3DS already had an install base approaching 15 million so market saturation started to kick in causing a large drop in year 4 despite still selling strong.
I think the sales curve for Switch will be different
Instead of large increase followed by small decrease followed by large decrease, I think Switch will be small increase, big increase, small decrease in year 2, 3 & 4.
When the herd loses its way, the shepard must kill the bull that leads them astray.