I forgot to mention that a price cut is very important for the Switch to outsell the PS2 mainly because the Switch at least compared to the DS and PS2 is struggling to sell as well in Europe.
In both NA and Japan however the Switch will inevitably be #1 all time in Japan by a comfortable margin and either #1 or #2 in NA, but will outsell the PS2 in NA as well.
The primary Achilles heal that may prevent the Switch from being the #1 bestselling globally is Europe, it's pretty far behind the PS2 and DS over there. The primary reason is cause the Switch tends to be more expensive for several countries in Europe since in certain countries a 3rd party distributor sells the Switch, not Nintendo, and for the distributor to make profit they make the Switch noticeably more expensive. It's a big reason why Europe's sales tend to react far more to price cuts then the other two regions. The Switch is still expensive in some areas of Europe to make it as appealing as the PS2 and DS were, where those consoles were dirt cheap. Even a 50$ price cut could go a long way