Without a price cut I don't think there's a way to reach 12m, let alone 16m.
Sure, there are system sellers (Splatoon, MK8, Zelda, Mario) but nothing seems the new Brain Age or Wii Fit, and it totally looks like they'll sell not so great (like a couple millions imho) until fall due to the lack of software.
We'll see, there's certainly room for a cut, but planning it this early would be strange and not so different from the panic move of July 2011. Other than that I don't know, 16m is a great amount for something which still has to prove itself as a desired product in the mainstream market.