The big question for me is how many units can NiN make per month and how many handheld gamers are going to buy into Switch?
NiN doesn't have to rely on just console gamers buying in this time. (Which truthfully isn't fair to directly compare it to PS4/XB1 sales since they are locked into console only)
If enough handheld gamers buy in, then Switch numbers could remain high for quite sometime. Price and lack of software however may hold many people off from buying Switch sooner than later.