3D as sustaining innovation (Sony cycle) = blow a bubble, put it in every piece of hardware possible, huge marketing push, sell to enthusiast, move downmarket, make it standard, then grab the royalties. Low-end market totally not interested, what's mine benefit? Prettier picture? Nah. Might get it when it's cheap.
New values of 3D tech in gaming (Nintendo? Hopefully, if not... I pass) = built it into gameplay, make it fun, differentiate yourself, sell millions games on that.
UPD: Regarding DS userbase in US, just read what Iwata has to say about it: "This graph shows Nintendo DS' consumer composition based upon our most recent survey in the U.S. Compared with Japan, the adult portion is not yet fully expanded, and we see further growth opportunity there. As I said, the DS ownership ratio to the population in the U.S. is just about half that in Japan, so there still must be the room for the expansion" - it's basically Japan userbase graph couple of years ago, the higher penetration - the more non-gamers, i.e. adults will join DS audience. In fact, DS userabse in US already is quite spectacular >50% are >18yo, and without doubts great majority is older than 8-9yo.
