I don't know why you'd say that Nintendo is afraid of iOS. Or rather, the reasons for them being afraid of mobile platforms is a little different than you are implying. During Iwata's keynote at GDC, he spent a while talking about these platforms and how they are saturating the market with low-quality games that are bogging down the industry as a whole and lessening the value of big budget, well-produced games made by your more traditional gaming companies. He's afraid that the value of content will decrease as the amount of content available increases, which is certainly a valid concern.

If you meant that Nintendo should be afraid of the massive success of iOS, then yeah, I kind of agree. Still, making a sequel to a monumentally successful mobile game on the most successful gaming console at the moment (or its 3D successor, due to launch soon) would hardly be a bad idea. Yeah, lots of "non-gamers" love Angry Birds, but that's the same market that Nintendo had been going after with the DS in the first place (remember Brain Training?).