I think the bigger question is where will Sony be in 5 years?
They seem very directionless of late and at least Nintendo has a plan. I have a lot less confidence in Sony's current direction, and unlike Nintendo they don't need Video games.
If Sony's next playstation flops and they have to exit the business (entirely possible I fear), I could see Japanese developers flock back to Nintendo.
But if that doesn't happen, I dunno where Nintendo is.