Yes, but neither are they going to become just like Sony/Microsoft all of a sudden. You also forget that this isn't the first time Nintendo has switched hands but also retained their identity as a brand (comparing Hiroshi Yamauchi's tenure versus Satoru Iwata's).
You have to remember Shuntaro Furukawa still has to answer to the board of directors, and one of the key points he raised that, while they don't think high-end hardware is off the table, they will still make sure their products have that distinctive Nintendo approach to them.
Naming something "Switch 2" is quite the opposite of that approach: It's very derivative and generic, and something more akin to what Sony would do.
Even Microsoft (much to some people's chagrin) didn't call their successor Xbox consoles "Xbox 2, Xbox 3, etc." and instead went with "Xbox 360, Xbox One, Xbox Series, etc.".
Not to mention calling it "Switch 2" can lead to a lot of confusion, like when being asked if a game is compatible for "Switch 2", making people lead to believe it requires, quite literally, 2 Switches.
No one saying they will become Sony/MS and its not point about Switch brand or Nintendo identity (and they dont change "Switch" brand by adding letter in name), but about most practical and logical naming, very informative and clear without confusion.
Saying that Nintendo is losing identity by adding number in naming is quite reaching.
Nintendo before usually named their console based on concept, having on mind that main concept (hybrid) will be main thing even in next gen Switch,
Switch 2 naming has even more sense.
For MS would also be much better if they had number in naming, everything after 1st Xbox was from "not best naming" to bad, I mean, Xbox Series X and Xbox Serie S naming, after Xbox One, Xbox One S and Xbox One X, is terrible.
Sony (Playstation) has easily best naming, because it's very clear and simple.
I dont see any confusion with Switch 2 naming, Nintendo on reveal would provide every information needed, and on every game you will have for "Switch and Switch 2" or just for "Switch 2", Nintendo done before that with New 3DS, nothing new, other namings could actually make more confusion.
Also, saying that next gen hardware with naming Switch 2 would make confusion is not good argument in world where we have Wii and Wii U, or 3DS, 3DS XL, 2DS, New 3DS, New 3DS XL, New 2DS XL.