Hmm, i would say there was the usual drop for a month or so, but that the Wii and DS just stayed low for longer compared to the others, partly because of the numerous price cuts/remodels and highly anticipated games being released during the lack of anything for Wii, and anything significant for DS.
So no, i wouldn't say there was a proper lull either, but i would bet at a different time of year all the attempts by Sony (and Microsoft, though they didn't really focus on Japan) to increase sales would have helped a lot more....yet during the yearly low sales period, they didn't even manage to get PS3 to outsell Wii for a week even with nothing holding Wii up....and PSP slim certainly helped sales, but didn't manage much even against a low DS.
PS2 probably survived through the whole period because of it's age, and the 360 is hard to use as any evidence, because it is recently seeing increasing popularity in Japan as it shakes off the original XBs shackles.
not sure i made any sense.
