History will determine WiiU's gen status.
If WiiU continues to stalls, only ever has current gen 7 ports and is replaced quickly, history will view it as in competition with PS360 and therefore Gen 7.
If WiiU picks itself up, starts having good-great sales, get next gen ports and lasts at least 5 or more years it will be considered a competitor to PS4/720 and Gen 8.
It is not unprecidented for two seperate consoles from the same manufacturer of different power to be lumped together - Atari 2600, 5200 - both gen 2. So if WiiU fails to compete with Sony/MS (and possibly other's) new systems, it would fall into this same pattern as Atari had.