Before the Wii, claiming their home consoles were on the decline was a legitimate statment :P NES (64 million) > SNES (49 million) > N64 (33 million) > Game Cube (22 million).
If the WiiU's sales don't pick up, and considering the Wii's popularity was "short lives", calling it a fluke would be a justifiable statement. I don't agree with it, but you'd certainly be hard pressed to argue the logic.