Miyamoto knows what he is talking about.
That doesn't mean everything Nintendo creates will be successful, though. As the Wii U clearly proved. Not every blue ocean is a particularly attractive one. It's always a gamble on whether the time is right.
I think Kimishima is a good choice for president, as he gets the whole idea of Nintendo, while also being an efficient and pratical business man who understands the value of good bonds with investors and developers. Miyamoto, in his infinite focus on functionality and player response, needs a bit of a counter balance for products to ever come out and meet the reality of the market.