I think it is (and has been for several weeks now) a result of the upcoming Move. Japanese love new consoles/gadgets, and Move is one, hence why (imo) the PS3 should have gone down much more lately yet didn't. And (in Japan) maybe Wii buyers are not buying as many Wiis also in anticipation of Move. We'll ses next week how much of a hardware boost PS3 gets. If it's a lot, that will be in my eyes possible proof that what we have been seeing for some time now was the Move effect.
Currently Playing: Shin Megami Tensei: Devil Survivor Overclocked, Professor Layton and the Curious Village
Anticipating: Xenoblade, The Last Story, Mario Kart 7, Rayman Origins, Zelda SS, Crush3D, Tales of the Abyss 3DS, MGS:Snake Eater 3DS, RE:Revelations, Time Travellers, Professor Layton vs. Ace Attorney, Luigi's Mansion 2, MH TriG, DQ Monsters, Heroes of Ruin