If history has taught us anything, it has taught us that a company can be on top and seemingly unstoppable, and next generation they are in last place.
Nintendo is not invulnerable. They can't afford to get complacent. No matter how great they may be doing now, everything can change extremely quickly.
That being said, I don't think they have anything to worry about for the rest of this generation, as long as they stick to their current strategies of blue ocean and disruption.
As far as Apple competition, I don't see them as a threat.







