I don't think why everyone thinks it will be called Switch 2. Nintendo never set a number behind its systems. When i worked in a videogamesstore there was one guy from Nintendo distribution calling it Switch Up. That was long ago. Back when people called me crazy for predicting a later release date than march 2023. Even back then i would have bet my head that there would be no earlier release date than march 2025. 

Back to topic: I don't think its called Switch 2. Of course there is a possibility but i don't think its a lock. I remember Nintendo DS 2, Xbox 2, PSP 2 and we know how that turned out.

I am not saying 100% it will be called Switch 2. But that is the easier name to use for now till it get announced (if it actually different name). But Switch Up is not confirmed either. And in cases like these it's just easier for everyone to just put 2 and use it as it is. It is why also the system after DS was called DS2 before it got announced, the same with xbox 2 psp 2 and so on.

Of course Switch Up is not confirmed. It was a Nintendoguy some years ago that had a meeting with workers in the store i worked who called it Switch Up. And that would be something I think is realistic Nintendo COULD POTENTIALLY do by calling the sucsessor like that. I think the reason for MS not to call the Xbox 360 Xbox 2 is because they do not want to have an inferior name (3 is more than 2) and the stupid uneducated masses would think the PS3 is more advanced than the 360 but both where basically equal. Nintendo had every reason to fear a potential PSP2 could equal a DS2 so 3DS had a higher number in the system's name anyway. They could not have known, Sony called it Vita and not PSP2. 

Because it's not confirmed, it's more okay to say it as Switch 2, for the time being, since everyone is doing it, and is the natural way of name it, at least till Nintendo officially announce it.

Even if i think Switch 2 is boring and not something Nintendo would do, you made a good point. But there is also at least one system that contradicts your theory. Did you know that before the Gamecube was anounced you could preorder it? In the computer the employee typed in your preorder there where even (rumored) Gamecube games that could be preordered. "dol Mario is Missing 2" was one of them. "Dol" stood for the official codname "dolphine" and we all know what "Mario is Missing 2" stood for.

My is not a theory but a simple fact. It's easier to just call a successor with the number 2 after, before it is actually announced. Since everyone is doing it, and that has no connection with the pre-order thing you wrote. What is the point of you mentioning it ?

Since when is Nintendo doing what everyone is doing/ suspects them to do? The name was not the reason WiiU flopped. It was a whole shitload of other reasons why it did. I just have the feeling Switch 2 is absolutley not set in stone.