Well, when Nintendo go under next generation, at least Miyamoto can go work on Angry Birds.
Even if the Wii U totally bombed, they would still be fine. They have about 10 billion dollars in cash right now. If anyone is likely to go under it would be Sony, they have been losing billions for years.
Before retirement Iwata will take the money and run, he still needs to pay his debts to the Yakuza for the Gunpei Yokoi hit he put out.
Not that I believe in Karma, but add an emerging giant virtualboy rising in the sunset as the Yakuza get their due, and damn that would make me a believer