Anything under 5 million is fail to me. Cuz Wada promised me it would outsell FFVII.
All jokes aside, there's little way to guage how the numbers will turn out for this title. People tried to guage FFIX, X and XII based on previous popularity and performance of the series and were all wrong, because the consoles weren't the same as previous titles and the fanbase for the series kept getting smaller each title. A conservative estimate would put a pre-order draw for the US at around 500-700k while it could get up to 1.5m. With a series as random and front-loaded as this, its anyones guess.