Well, it certainly doesn't sound like they're half-assing this. I'm interested to see what they come up with.
I think Iwata sees mobile devices as an entirely separate medium from gaming devices. Similarly to they way they are seeking partnerships with Sony and Netflix for film and television based on their IP, they are partnering with DeNA to bring their IP to mobile. It isn't redundant alongside their Wii U and 3DS offerings, any more than the Pokemon Trading Card Game is redundant alongside the video games.
He's been saying for years now that he thinks the mobile market is less of a competitor with Nintendo's products and more of an opportunity for them to spread awareness and expand their business. Until now this didn't include making games for mobile, but I think he has recognized that there is demand for mobile games and that they can exist independently from games for other hardware. Nintendo has no plans to make phones, so in order to get into that medium they'll have to partner with another company and release games on someone else's hardware. The same way they have no plans to create their own film studio, so they have to partner with Sony to make movies.
