Saw this over on NeoGaf

December 28, 2012, page introduces PlayStation 2 Sony Computer Entertainment (SCE) ( here at that), shipments of the PlayStation 2 in Japan has completed has been announced today. Thus, what is new is only left in the market. 
PlayStation 2, released on March 04, 2000 as the successor to the PlayStation. While performing a model change, such as power saving and miniaturization, as popular game hardware stationary, it is supported by the game fans over a long period of time. In addition, since the DVD player also has the ability, I also helped its spread. The worldwide cumulative sales of more than 50 million 100 million.

http://www.famitsu.com/news/201212/28026636.html

Sony currently has the PS2/PS3/PSP/PSV and soon to be PS4. I'd imagine it would be hard for retailers to keep stocking so many systems in Japan, they have to cut something. They also have to keep stock of the DS (although they aren't really replenishing stock of this), Wii(will probably fade out the longer the Wii U is around), 3DS and Wii U. MS only has the 360 in Japan and it doesn't sell that much so keeping much stock isn't a problem.

They are also still releasing games for the 360, so that is not a problem. On the other hand I haven't seen a new PS2 game released in ages. The PS2 game sections in stores is also slowly dwindling.

RIP PS2. I've owned several JP PS2's over the years. I still have one JP PS2 under my tv now.

Microsoft wants to keep fighting its losing battle. Sony wants to accept the end of an era and pave the way for future success.