Iwata has said in the past, very recently too, that he believes in forming partnerships. If they were to go out an buy a bunch of studios - which they could, he mentioned - then the creative talent might leave...so what's the point?
He said its better to form partnerships, and you can see his methodical approach in the past with not burning bridges but rather handling things in a very behind-the scenes approach, and using Nintendo's strengths to create strong relationships which then lead to other publishers being more inclined with forming said partnerships.
Case in point, we have Nintendo doing this with Tecmo Koei/Team Ninja, Capcom (Monster Hunter) and Square Enix (Dragon Quest)
He also said they would invest where it made sense to do so, hence the acquisition of Monolith Soft and of Retro way back in the day.
Nintendo isn't like Microsoft or Sony in that manor. That doesn't mean MS/Sony's approaches are bad either...look at the slate of mass market exclusives they have as a result...but Nintendo's philosophy is simply different, and it will probably pay off for them in the long run in a different way.
I wouldn't expect Nintendo to own these IPs at all. But Nintendo certainly has an interest in slowly becoming the defacto video game system. I think Iwata wants NES/SNES levels of third party support all over again, and his business moves show he understands what needs to be done to form the correct relationships to move in that direction