I think the universal OS/mutilple hardware sharing the same APIs is bloody good idea for Nintendo, to be honest. It'll go a long way to solving their crappy software output.
Less of this...
Team A - Console Mario Kart.
Team B - Handheld Mario Kart.
Team C - Console Zelda.
Team D - Handheld Zelda.
...and more of this...
Team A - Console/Handheld Mario Kart
Team B - Console/Handheld Zelda.
Team C - Console/Handheld Terranigma.
Team D - Console/Handheld Secret of Evermore.
NCL might not be set up this way, but you get the general idea.
I really don't think/hope that's what Nintendo is planning to do with the shared architecture.
Can't really talk for everybody, but the kind of experiences I enjoy on home consoles and those I enjoy on handhelds are quite different from the most part.
While this strategy is great for Smash, Mario Kart and possible Mario sports spin-offs, I don't think it's a great idea. Would Zelda ALBW been that critically acclaimed if it was a home console game (obviously with the "adequate" graphics)? Alternatively, would a game like Zelda U be really enjoyable on a handheld?
Besides, what Smash Bros. showed us is that even if the home console version is far superior to the handheld version, players will always stick to their favorite platform... so a shared architecture wouldn't help home console sales in Japan (or handheld sales in the West) if Nintendo's just going to make the same games for both platforms.
I mean, we've already seen it several times with the Sony ecosystem: when there's a game coming out on both PSV and PS3, the userbase is split, there's little (to no) increase at all.
What I think (hope) Nintendo will do with a shared architecture is more in those lines:
1) games like MK developped for both platforms
2) scalable engines, so you could have Zelda 4DS using the same engine as Zelda Wii W, cutting down on dev time and using less ressources.
3) potentially "upgraded" versions of games later down the road for some games that could work well on both home/handheld consoles.
4) actual cross-platform offers. Don't make people the same game twice.
They need not forget to make experiences catered for each platform (when it makes sense), or people will just stick with their favorite kind of platform (like players did with Smash 3DS).
But the most important aspect of Nintendo's next-gen strategy is the whole "account relationship", so that there's no "resetting" when a new gen is launched.