From a combined 250 million sold units with the Wii/DS shrunk to barely 80 million with WiiU/3DS.
Will Switch really be a success with only 80 million lifetime sales, if it reaches that number at all, knowing it's the only Nintendo platform going forward? 80 million wouldn't have been a growth but stagnation over last gen.
A lot of that market went mobile or left altogether.
A good portion of that market is overlap, as well - Wii and DS owners.
The way I see it, the main benefit of the Switch isn't that it will sell more units than the 3DS and Switch combined (hopefully it can match it, though). The main benefit is to reduce operating costs by not having to support two systems - one dead weight (WiiU) - and selling software to a combined platform at a higher price. Rather than 13M people potentially buying six $60 games and 65M people potentially buying eight $40 games, you can have 80 million people all buying a dozen $60 games.
$4.8 BN in potential gross 1st party software sales versus $3.4 BN.
That's two BIG ifs, though.
1) Can Nintendo move 80M Switches?
2) Can Nintendo concentrate their efforts into a steady release schdule with roughly a dozen 1st party titles a year?