These are 3DS shipments year by year:
FYE March 2011: 3.61 million (small launch window)
FYE March 2012: 13.53 million
FYE March 2013: 13.95 million
FYE March 2014: 12.24 million
FYE March 2015: 8.73 million
FYE March 2016: 6.79 million
13.95 million/year was the 3DS' peak.
You can say Switch will capture some of the Wii U audience, but a lot of Wii U owners owned a 3DS, so that maybe gets you only 5-6 million unique Wii U only owners total.
100 million is not happening barring Switch getting a huge break out new IP like what Pokemon was to the Game Boy or Wii Sports to the Wii.
Nintendo has work to do to even get back to the level the 3DS was earlier in its life cycle. I think what you see in the drop off from 2014 to 2015 is the large impact on many more dirt cheap tablets flooding in to kids.
I think it needs to have Android apps.
