That is a good point. At least some of those people won't have used an Xbox since the 360 so it's an opportunity to get back some customers that the Xbox One lost. 

Possibly but the chances are if they were looking for a PS5 to begin with, they would have played on PS4 at some point as that community is over 100M. For a lot of people Sony's 1st party is just too good to pass up "forever" as their brand is too strong to ignore. 

That's not true. In 2016, people were much more pessimist about the Switch's prospects, here's  a thread from October 2016

https://gamrconnect.vgchartz.com/thread/221574/early-nintendo-switch-sales-predictions/1/

Yes, you could have. You could have been Lawlight and predicted a hard firm 20M.

Brand loyalty only goes so far though.  Sony did manage to lose 70 million+ customers in a single gen going from PS2 to PS3.  I know that it's not remotely the same situation.  But, it does prove there were tens of millions of people who bought a different console that gen and never felt the need to go back and purchase a PS3 later.

Man, I remember co-workers and friends that were claiming the NX could do nothing to save Nintendo and that they should do what Sega did, and go third-party lol. Aged like fine milk xD

Same here!  And that very same co-worker ended up calling me much later to tell me that he was at the store buying his daughter a Switch for Christmas.

You're right, it's not the same situation at all. PS3 was a different beast altogether and that was Sony's fuck up. There's a world wide chip shortage going on and some gamers are being hyperbolic because shipments weren't high enough this month for their liking. There's no PS3 mistake here at all and they're selling on par with PS4 at the moment.  

I’m pretty sure myself and a few others predicted 100+ million since the NX days based on what Iwata was saying about it.

One of the biggest challenges Nintendo faced was that increasing development times/cost/manpower, with their handhelds making the jump from 2D to 3D and their consoles from SD to HD, was making it too difficult to support two separate platforms at the same time and it was only going to get worse.

On top of that by this time it was pretty clear Sony wasn’t no longer interested in the handheld market so Nintendo would be able to absorb that audience as well. Individually 3DS, Wii U & Vita we’re all lacking in 3rd party support but when those markets were combined it became a very large and well rounded library.

3DS+Wii U+Vita did 100+ million so it was never unrealistic for a platform that replaces all 3 to replicate that.

I'm not convinced PS5 has lost many sales in the long term due to the current shortages; I expect people will simply get one further down the line instead, there will ultimately be a many PS5 games you cannot play on Xbox Series.

I don't know if I'd go so far as to say it's guaranteed; Nintendo's tendency for moronic self-sabotage could always resurface and they could replace it next year and quickly discontinue Switch 1 like Sony have with the PS4.