Nintendo can sell multiple Switches because there will be multiple versions of Switch as time goes on. I agree that parents would be less inclined to buy multiple Switches for the reasons you stated. Switch is more amenable to being "shared" as a system than the DS/3DS are, that said Nintendo can bend the rules there and offer more frequent hardware refreshes of Switch, thus creating other incentive to have multiple units in a house, the same way Apple and other mobile makers get such high sales ... you think if they just release one iPhone every 5 years they'd have even 1/2 the sales? Nintendo will adopt that upgrade process to a degree IMO. You'll have a higher end Switch model in about 3 years IMO.
That said, any hardware is in tough if the goal is PS2/DS or bust. That may very well never happen again not in the way it did then. Even the PS2, needed like 10+ years to hit those sales, DS did it much less time. There's a good chance you'll never see anything like the DS again, not from Nintendo/Sony/MS.







