I think this is actually great for Nintendo and NoA, specifically. Performance in North America, which has seen much better days, will now fall directly on Iwata's shoulders. Those who want NCL to pay more attention to the NA market should be far happier with this situation rather than a no-name (or at least less well-known and less influential) NoA CEO because now if things don't turn around in North America, there will be no one to scapegoat. The man in charge of Nintendo as a whole and credited/blamed for ALL of NoA's performance will be one and the same. What's the sense in appointing someone else to NoA CEO who will most likely continue to be brushed aside as NoA seems to have been lately?
I'd bet Iwata will do all he can to focus on cleaning things up in North America and it will not be the afterthought it seems to be now. Whether he's able to understand the western market is another story. however, as long as Iwata is still around, I think him taking direct responsibility and a much larger stake in NA should be seen as a good thing.