I think it will do about as well as the 3DS (maybe a bit better, maybe a bit worse) from where I'm standing right now, but it's hard if not impossible to make any kind of reasonable prediction at this point. Just too many unknowns.

Are we even sure Nintendo is going to handle the hardware in a traditional manner? What happens if there's a Switch 2 ... in like 2 years? What happens if they adopt an upgrade model more akin to tablets or smartphones? Old model becomes the cheaper budget model, new model rakes in new adopters, software library works on all devices.

Where's the poll on holiday?

I'll give 80m as my prediction given it's unified nature.

70 million, something like the 3ds

Why make a Switch 2 in 2 years when they can do it in 5 or so years when the same tech out in 2 will be much cheaper giving them more control on pricing, right now a traditional type of handling makes more sense. A NSW2 in 5 years that hovers around PS4 level of performance on the go should be afforadble and still a large jump than releasing upgraded model every 2 years.

90-100 million.

The hybrid concept will appeal to more people than many think around here.

50-60M

PS4 tier mobile chips will be available by next year actually. The tech is moving very fast. Nvidia has already finished the Parker, which would be the successor to the Switch's Tegra X1 ... they are now well into development of Tegra Xavier, which will debut in 2019 or so. The Xavier chip will give you PS4/XB1 tier graphics. 

The model ranges may be different Switch 1/2/3 may not be it, you might have Switch Pro, Switch Alpha, whatever. 

60 to 70M is a safe bet, maybe more.

I will go further, 15 Million after 1 year on the market (March 2018).

I know such chips will be available and very likely so do Nintendo but I doubt they'll release NSW2 in 2 years instead I see them using that tech in 5-6 years giving NSW a good run while the successor will be vastly affordable by then as well falling more in line with their company approach. This is why I don't see SKUs with differing chipsets as well, it's not only easier for them to manage but also for their consumers.

People seem to forget that 3DS keeps selling like hot cakes and has a 200Mhz GPU... for god sake, once and for all try to understand that SOFTWARE SELLS NINTENDO MACHINES! Not hardware.

Put 3DS side by side with VITA and check the differences. Now look at Wii U and ask, where are all the main IP's? Where is Monster Hunter, where is Pokemon, where is Animal Crossing, etc... thats right... they wont make the same mistake again.