Sure, one of the main issues with Nintendo has been that their audience is split between their handheld and home console ecosystems. On top of that Nintendo software teams have had to split resources between 2-4 different platforms.
For example, in 1999/2000 Nintendo was working on late GBC & N64 games while also working on early GBA & GC games. In the 2004-2006 period they would have been working on late GBA & GC games while also working on early DS & Wii games then around 2009-2012 they had to work on late DS & Wii games while also working on early 3DS & Wii U games.
That means each generation only gets a few years of Nintendo's full attention and even in those years support would be split between handheld and home consoles. This progressively has gotten worse as development costs and times increase.
Switch is the first time since the mid 80s that Nintendo gets to give 100% of their support to a single platform which means their audience will all be in one place and sales will not plummet or stagnate like many previous devices have.
I'm not saying it will pass PS4 but 100-120 million is not out of the question at all.
I fully expect 100m but the PS4 is already past that. The question Im asking is how big is their audience full stop. Fundementally how many people are interested in what the Switch is and its line up of games? Looking at all big titles its the typical pokemon/mario/animal crossing/zelda etc. The Switch is doing amazingly well at tapping into Nintendo's audience but that could just mean its front loaded.
Even with consistent support up until 2017 the 3DS reached a natural saturation point around 80m. What will that be for the Switch?
Well no, you asked if there are 100-120m people who want to play Nintendo games. I'm saying yes there are.
3DS was only moderately successful outside of Japan, this is not the case for Switch. Switch is doing significantly better than 3DS in America, Europe and especially Other regions.
For example, at their investor meeting last January Nintendo announced that Asia (not including Japan) made up 1.4% of 3DS sales while it makes up 7% of Switch sales.
That means that in almost 7 years 3DS sold 1.1 million in this region while Switch sold 2.25 million in under 2 years.
These regions have grown so much that Nintendo has decided to seperate Europe and Other into 2 separate regions in their quarterly reports (they used to be blocked together).
80 million may have been the saturation point for 3DS but it is not for Switch as it is a mainstream success in every region.