The Wii was a juggernaut during Nintendo's last console generation. Since going on sale in late 2006, it sold 100 million. Now, it seems those days are over. For good.
On Nintendo.co.jp, the Wii page reads, "Manufacturing is scheduled to end soon" ("kinjitsu seisan shuuryou yotei" or 近日生産終了予定). In Japan, Nintendo has been known to announce it is ceasing hardware production for certain consoles (or colours) via notices like this.
Stacked up against the Famicom, which Nintendo finally discontinued in 2003, it looks like the Wii's days were comparatively short. Its sales, however, were huge. Kotaku is following up with Nintendo and will update this post, should the company comment.