I remember this one. I was always one of those who remained skeptical of the Wii U, but I could never have imagined it would do as badly as it has, probably not even close.
I believe my first semi-realistic estimation with figures was 18-24 million, made some time in late 2013 or early 2014.
Here it is; http://gamrconnect.vgchartz.com/thread.php?id=171400&page=3
Late 2013, not nearly as impressive as the OP here though, even I had much higher expectations even if I was skeptical after learning more about the concept at E3 2012 (which is when I first mentioned properly that I thought the whole machine was a potentially terrible idea).
Kudos to the OP.