The risks I see are:
Nintendo is not handling the development for mobile smart phone games themselves. Quality may suffer.
The NX system may launch soon. This is a knee jerk response to the terrible WiiU. Any new console launch is a wild card.
Nintendo may be outspent in Virtual Reality by dramatically larger companies. Facebook, Apple, Sony, Microsoft, Google, Samsung.
Street estimates have nintendo doubling profits by 2017. So some mobile growth has already been factored in.
If Nintendo came out tomorrow and said it would become exclusively a software developer I would buy the shares instantly. But anybody who understands Nintendo corporate culture knows this is highly unlikely.
I'm still sitting back and watching.