The biggest franchise on the planet selling only 20k for Wii U on opening month does surprise me a little actually.
Even COD on Wii in Nov. 2006 (Wii launch) managed 48k with roughly the same userbase. And that was a heavily downscaled port from when the franchise was only a fraction of as popular as it is today.
I wasn't expecting sales comparable to the PS3/360 obviously, but these are very, very low.