Well, it looks like VGC is pretty spot on with Wii U tracking, with it having ~460K on shelves. Same goes for 3DS, with ~940K on shelves.
SM3DW is definitely overtracked, however. Nintendo has it at just over 1M shipped, while VGC has it at 1.5M sold through. So, it's at least 600K overtracked. On the plus side, Pokemon looks to be undertracked.