Here we go. this is the picture I was looking for. This was shown at the same time that the NX was announced. It was one of the slides during the conference. As can be seen, Nintendo doesn't seem to see the NX as a Wii U or 3DS replacement. Rather, it seems obvious that the intention is to supplement their current hardware lineup with some unifying piece of hardware that will likely lead into their next generation of gaming hardware. Basically, it can be seen as being intended to be supplemental rather than any kind of full replacement.
If it was intended to be a straight up home console, it would be made as a Wii U replacement. Nintendo isn't going to pull a dumb move like trying to support three dedicated devices at the same time, but they also didn't seem ready to accept the idea of phasing out their current hardware during the initial announcement in March.
