Like we always say playstations tend to have better legs then Nintendos. It's why we shouldn't expert switch to outsell the ps4. The ps4 sales have been stable as fook and its why for years the talk of has the ps4 hit it's peak year been nonsense. It doesn't have that traditional big peak and fast decline many products suffer from.
The Switch has many unknowns compared to previous Nintendo consoles or even just consoles in general. One of those unknowns is will 3DS customers and games moving to Switch change the dynamics ,this is tied to another unknown exactly how will Nintendo deal with the 3DS going forward , Nintendo Online should also help just like PS4 and XBOX ONE are the entry points to their particular ecosystems so is Switch to Nintendo's.