I still remember the 2 week period when wii sales began to decline. It was almost immediately after the Playstation*Move launched. Kinect came out 4-5 weeks after, and that was the beginning of the end.
Nintendo launched the wiiu early, knowing full well it was the only card they had. Get enough wiiu consoles out into the wild and hope developers and consumers respond positively during the 12 month lead. That was the strategy, all cards have obviously been placed in this strategy.