While we can all agree there are many factor's around WiiU's current sluggish sales, I think we can all agree on two primary ones:
It needs (major, exclusive) games - and these will come in time.
It has failed to spark people's imagination the way Wii did or the more powerful next gen consoles most likely will for the core.
Most people here would have told you Wii only had one game worth owning for quite a while - Zelda:Twilight Princess (which was also on Gamecube so no one needed to buy a Wii for it). But Wii sold primarily on Wii Sports and the excitement of motion controls. Clearly this isn't the case with WiiU.
Other factors include - lack of power, price, poor 3rd party support, poor focus, poor marketing, gamepad is putting off people, etc.
Based on these factors - what do you currently think Wii 's lifetime sales will be?