The Switch is helping offset the decline in sales of the PS4 and Xbox One. Nintendo has generally done their own thing over the years. Look at the naming of their consoles and handhelds, as well as their controllers.
Switch sales will likely decline while the PS5 and Xbox Series X grow in their early years.
Well you are kind of right. I think it is more accurate to say that PS5 and Series X will be out of synch with Switch. Switch launched about 3.5 years after PS4/XB1. Now the other two companies are launching about 3.5 years after Switch. Usually, competing systems launch within 1-2 years of one another. That didn't happen this time. The systems are out of synch now. We'll just have to wait and see what the effects will be.