I'm not expecting a true successor to 3DS until 2017 at the earliest, at which point they'll release some sort of home / handheld hybrid console. The 3DS family reaching 80 million lifetime sales is definitely doable.
Nintendo handhelds tend to stick around for quite a while, with GBA being a fluke since the DS was originally intended as a third pillar and not a successor device.
They say, "Evil prevails when good men fail to act." What they ought to say is, "Evil prevails."







