Two things could happen:
1) Apple will buy Nintendo or
2) Nintendo starts creating iOS games
I don't think Apple will buy Nintendo. It would kill their stock price. Apple tends to make strategic buys of small companies to leverage their technology in a grander scheme. Nintendo has too much baggage that does not fit with Apple's road map. Additionally, Apple would then be making games and competing with their developers.
I would not be surprised if Nintendo starts making iOS games -- especially in a deal whereby Apple invests to get Nintendo to port some of their games to iOS (possibly exclusively).
In most businesses revenue is king.... that chart isn't showing number of downloads...
The question to be answered is how much of that revenue is revenue taken from Nintendo and Sony versus market expansion. Many of the folks who buy iOS and Android games probably never owned a portable gaming device before.