A lot of you are exremely overestimating this game's sales. Here are some factors that usually hurt sales:
-The first installment of a series usually sells better than upcoming ones, so it'll be hard to beat TP for this game.
-Usage of the Wii Motion Plus could be hurting, it doesn't have though.
-Unlike the successful bridge games that were either Mario or new franchises, Zelda is either not known to casuals at all, or worse, known as a hardcore franchise that isn't for them
-the two DS games that had that bridgey approach didn't sell more than other games in the franchise, Spirit Tracks seems to sell even worse than PH.
All in all, I think if Nintendo tries to cater the casuals the game won't sell over 5 million because casuals will still not be interested in the game in huge amounts while hardcore gamers will be a bit reserved if the game isn't primarily for them.
If Nintendo is able to create a revolutionary game that still feels like a Zelda (As they did with OoT), they might be able to reach the 7-8 million range. I think everything north of 8 million is completely illusionary.