Switch didn't sell 150+ million because it had a "novel gimmick", it sold that much because the hybrid form factor made gaming accessible, convenient and appealing to a huge audience, and Switch 2 has that same form factor.

The successors to the consoles you list didn't fall short because their success couldn't possibly be followed up on, but due to their own specific failings and circumstances, from PS3 being overpriced and falling behind in games early in the 7th gen, to 3DS having to compete with the rise of phone/tablet gaming, to Wii U making basically every mistake imaginable.

As of yet, there's no reason for Switch 2 to sell far less than Switch 1. They haven't made any massive mistakes, nor has the market changed substantially.

Not sure if it can reach switch/ps1 levels.
But its 100% a 100mill

Perfect. Gimmick. In this case I am using gimmick in a much more broad term. Gimmick would be ANY selling factor beyond being a games console. PS2 with DVD Player? A gimmick, but a gimmick helped it to reached an audience that it otherwise would have not if not for said gimmick. 

Very very late response.

There was nothing one-off about the hybrid form factor though; the Switch 2 will have that exact same convenience and flexibility. If it only sold because it was novel, then sales would have crashed after a few years once it was no longer new and fresh, yet the Switch's legs have been exceptional.

Currently there's no evidence at all for a DS to 3DS drop.

Did I say DS to 3DS drop?(Honest question). CGI-Qualities estimates are mine as well. I do not believe that NINTENDO is going to capture lightning in a bottle TWICE ... in a row. No other console has ever done that with the same "gimmick". Then we have to think about how many of those people who bought Switch because of the cool factor; Do they still use it? Why would Switch 2 pull these people in? Let's look at PS2 to PS3; We know SONY fucked up but in some sense you could look that 90mill PS3s as "actually" PS fans(loyalist). That lost 70mill are users who were not loyal to PS(went to xbox)or those who just bought PS2 because of DVD or Madden

It takes a very unique set of elements to have a console go over 130mill. 

We know from Nintendo that the large majority of Switch owners are still active users.

In the examples you list like PS2-PS3 or DS-3DS there was always some massive shift that caused sales to drop; so far there is no such shift in the market going from Switch to Switch 2.

It's entirely possible that such a shift does occur, but so far there's nothing.

Here's is one thing that I don't think anybody is considering. Switch also has the edge that unlike traditional home consoles, households tend to have more than one. With Switched rumored to be $400, I highly doubt that families will be repeating that trend especially the economic path that America is headed towards.

Brother. Even if SONY did not fuck up on the PS3 it still would not have reached PS2. Nintendo Wii and XBOX 360 would not doubt would have still taken sales aways. The rise of PC gaming would still have taken away sales. Those things still would have existed with or without. When Switch came out it was the only thing doing what it did. Now we have dozens of these high powered handhelds. Both SONY and MS are hard at work on their own handhelds. Its more than just one major thing. All these little things could add up and instead of Switch 2 at 130mill its not 119mil.

Here's is one thing that I don't think anybody is considering. Switch also has the edge that unlike traditional home consoles, households tend to have more than one. With Switched rumored to be $400, I highly doubt that families will be repeating that trend especially the economic path that America is headed towards.

Brother. Even if SONY did not fuck up on the PS3 it still would not have reached PS2. Nintendo Wii and XBOX 360 would not doubt would have still taken sales aways. The rise of PC gaming would still have taken away sales. Those things still would have existed with or without. When Switch came out it was the only thing doing what it did. Now we have dozens of these high powered handhelds. Both SONY and MS are hard at work on their own handhelds. Its more than just one major thing. All these little things could add up and instead of Switch 2 at 130mill its not 119mil.