Generations are strictly historical terms, referring only to the time they were released. The 7th generation started with the DS, and included the PSP, XBox 360, Wii, PS3, iPhone, n-Gage, Gizmodo, Wu, Vii, and maybe even Facebook as a gaming platform.
The 8th gen just started with the 3DS.
Seriously, arguing these terms is like saying "I think the 80s started in 1975 because I feel it in my gut."