Most people think that when Nintendo says "We make games that try to appeal to all people" they mean one game can appeal to all people. That's not what they're saying at all. They're saying that our platformer game will appeal to all people who like platformers. Most people think Nintendo should specialize and gather more resources to develop more types of games. These people haven't been paying attention. Nintendo makes rpgs, adventure games, puzzle games, strategy games, sports games, fighting games, racers, party gamers, shooting games, platformers, rts's, and even horror games. Most people think that pandering to third parties is the only way for Nintendo to be successful. That is obviously false when they are the largest company in Japan. They are seen as unsuccessful but they are the most successful company in the business today.
So why do people continue to complain? It is because Nintendo doesn't make mature games anymore. Why? Because it is not their philosophy anymore. People are waiting for Nintendo to develop a mature FPS. It's never ever going to happen, at least not with the DEVELOPED BY NINTENDO moniker on the front.
And I think people realize that. That is why it is so exciting (or frustrating) to speculate who Nintendo can go to and buy or partner with to make mature games. And I agree with that sentiment, but I don't believe they need to go to a new developer (just yet).
Nintendo first needs to prove to themselves that those markets are viable. Obviously they see the success of COD or GoW, but they also see the cost of all those who have tried; the companies that shut down after one big game didn't sell. Still, they need to prove to themselves that targeting a specific demographic is not only possible, but mass marketable. They need to employ their same philosophy "We make games that appeal to all people" and use it not with genres, but with demographics. Nintendo should make a game that appeals to all 40-60 year old women. They should also make a game that appeals to all 18-35 men.
Make a new company brand to go with this same, but skewed philosophy. Make it the Miramax of Nintendo. Invest in it as much as you would anything else. Start small and work diligently until you can bolster that new side of Nintendo as much as the old side (either through the building of new teams or purchasing companies) and work together to reach every genre and every demographic simultaneously.
That is the way I see Nintendo succeeding in the future. The have the X and Y axis. Now all the need is the Z.