Dear lord, given the recent information that there will be a 1 million initial shipment, I have pretty low expectations for this game's sales.
1 million first day
1.3 million first week
2 million lifetime
Because of the 1 million initial shipment, I think this title may have some "legs" relatively speaking. Instead of 2 million, it could sell 2.5 million. It's the first iteration of Final Fantasy this generation. Looking back, the first iteration of a Final Fantasy in the previous two generations sold more than its successors for the respective generation (VII almost 4 million, X 3 million). I have hopes this could do 2.5 million, but I'll go with 2 million. Depending on what it does in Japan, it could do 5 or 6 million worldwide on the PS3 alone.
2011 Predictions
Wii: 17m (100 million total)
360: 13m (63 million total)
PS3: 15m (61 million total)
