I remember well before Nintendo even unveiled the Switch when the Eurogamers and Emily Rogers rumors started coming out revealing that the NX(Switch) was a hybrid console with detachable controllers powered by NVIDIA's Tegra GPU. At the time, these rumors made me initially really optimistic about the NX(Switch) because while I always thought Nintendo should make a powerful conventional system that gets good first and third party support that directly competes with Sony& Microsoft, I always had faith that Nintendo having a hybrid console would work for several reasons:

1.All of Nintendo's game development studios would have to make games on one platform, which means there would be far less game droughts and the stronger software as a result of combining all their games onto one platform would make it much more appealing for consumers to buy the NX(Switch), since games sell systems.

2.The increased sales of the Switch as a result of stronger 1st party software would motivate 3rd Party developers to make games for the NX(Switch) due to the larger install base they could make money off of. Along with the Switch being somewhat closer to the power level of a PS4 than the Wii U was, and using an off the shelf architecture familiar with developers. It would've made it easier for 3rd Party Support.

3.It would essentially be a Nintendo handheld, and Nintendo handheld's have always sold like crazy as Nintendo KNOWS how to make handheld's that sell. So I would expect Nintendo to bring over their handheld expertise to the console side to sell more units.

However, after Nintendo unveiled the Switch and we've started getting leaks that the Switch would have only 4GB of RAM and would be using an underclocked Tegra X1 Chip instead of an X2. Along with the fact that the Nintendo Switch Presentation really gave me vibes that Nintendo didn't really learn from the mistakes of the Wii U by trying to appeal to a casual market with focusing on motion controls and games like 1-2Switch, along with the lack of major 3rd Party games shown in the presentation, it later made me doubtful that the Switch was going to do very well, and all the negative press surrounding the Wii U & Nintendo at the time sort of clouded my image of Nintendo and made my prediction of the console more pessimistic than it should've been.

In my mind I thought, why would anyone from want to spend 300$+ just to play Nintendo's first party titles with little 3rd Party Support with only Zelda as a launch title, on a system that's significantly weaker than the PS4/Xbox which were also priced at around 300$ at the time. While I did think it would sell better than the Wii U cause the marketing was better while being a handheld and an objectively better system hardware wise over the Wii U, I was still rather pessimistic it would sell all that well. 

Even looking at it on a handheld side, while Nintendo handhelds have always sold well, I thought the Switch would be too expensive for handheld consumers to want to buy it and I wasn't sure if they'll be interested in the Switch's ability to play "Triple A console games on the go" since handheld players usually would rather play pick-up and play games and the PS Vita tried to offer that console gaming on the go experience and ended up failing miserably, making me believe the Switch as a handheld wouldn't do as well.

Also, initially it didn't seem like Nintendo was originally doing their "combination of games on one platform" as I hoped since they were still persistent on supporting the 3DS, which made me believe the Switch wouldn't have a great software lineup as I hoped which would limit the sales.

However I still thought it'll sell better than the Wii U since it has much better marketing, a more impressive system and STILL technically a Nintendo handheld despite all I said. Also, I predicted the Switch would get a Pokemon game which i felt like would boost up the sales.

My prediction for the Switch at the time was 30M sold in it's lifetime, which isn't terrible and Nintendo could probably make a profit off of those sales. However it was still far from being a major player in the gaming market as it's market would look niche compared to PS4/Xbox and not enough to get good 3rd Party support.

Thankfully, I was completely wrong as Switch is currently going to be one of the greatest selling systems of all time, and I'm so happy to see Nintendo bounce back after the disaster of the Wii U.

Less than 20 million.

After four agonizing years of the Wii U, it felt like Nintendo had completely lost the plot and were in an irreversible tailspin.

I've never been so glad to have been wrong.

Pre-announcement of what the Switch actually was I was guessing 25-30m. After the October 2016 event that showed the concept off (really fucking well) my prediction leapt to 75-100m depending on games. I'm confident in 120m+ now.

You guys had no faith. After seeing first main promo ad for it i would have said 60-80 least.  It was obviously not Wii u after seeing marketing for it.  There is no way Nintendo would go from 2 to 1 system and end up in Wii u situation.

I predicted it to be the best selling console of all time based on the October 2016 trailer alone. It gave me Apple iPhone introduction vibes. The iphone wasn’t the first touch screen device but it made things simple and easy. The switch wasn’t the first modular console device with detachable controllers.

So many companies have tried the controller attached to the screen thing but it was never as smooth and seem less as the switch itself.

The future is in the switch. The concept of portable and stationary device isn’t just for gaming. This is by far the most successful computing device to do that. Microsoft tried with Windows Phone (flop). Samsung is also doing it their android phones (flop).

Apple is in transitioning mode with MacOS and IPad OS.

And arm soc is the future. Every laptop and computer will transition eventually. Intel/ X86 should be very sacred.

Nintendo really thought so far ahead of every one else. The switch is a portable/stationary computing device with an arm chip.

I was shocked to how many people were down on it.

I expected 75M.

At the time I thought more would be very difficult to sell more than that at a $300 price point and feared Nintendo would have been forced to do the same as they did with the 3DS, meaning a massive price cut early in it's life that wouldn't have left much room for future price reductions. Glad this turned out to be too pessimistic and an early price cut (or any price cut within it's first 3 years and counting) was unnecessary.

It was partly a handheld and I figured all Nintendo handhelds always get great 3rd party support from Japan so I figured between 40-60 as I thought it might do worse than 3DS due to Smartphones but better than Wii U. Tho I was not expecting it to be a system I'd enjoy that much. I greatly disliked the 3DS. I got a Wii U for Xenoblade X and Bayo 2 and while I enjoyed other games on the system. I was glad when the Wii U era was over. Switch is my 2nd fave Nintendo system behind SNES. I love it as much as my PS4.

Around 60M. 20M coming from the home console target group (it couldn't get worse than Wii U) and 40M coming from the rapidely shrinking handheld target group.

I Remember PS5 being 100+M up to 120M, Xbox 50M up to 60M... Switch I don't remember if it was 35 or 75M, but obviously I was severely wrong on both. Perhaps it will do the sum of both.

At the bottom of this post is a link to a blog post I made August 25, 2016.  In it I predicted the success of the Nintendo Switch (or NX).  I also spent a lot of time explaining how the PS4 Pro (Neo) and XBox1 X (Scorpio) wouldn't do much.  There was a common narrative at the time that Switch would fail, because of the other companies' upgrades, and I was dispelling this myth.

I didn't give a number at the time, but I probably would have said in the 100m-120m range.  
https://thoughtfulmirth.wordpress.com/2016/08/25/sony-and-microsoft-lay-down-to-be-slaughtered-by-nintendo/