Not that i'm criticising you Moses. but i usually turn to vgchartz for sales figures. i'm not sure how reliable they are since they dont reveal their sources. but their numbers do usually line up with the figures reported by publishers and manufactures like Microsoft or Sony. and their sales figures for the DMC series are somewhat different:
i'm not sure which figures to believe, but i'm pretty sure the numbers they have for DMC3 are wrong because that has changed since i've been looking at the DMC figures as of last year.
but i wouldve assumed that those figures were indeed accurate, since (i think) Capcom have said they've sold 10 mil copies of the DMC series during the lifespan of the 4 games. so it seems to me aside from the DMC3 discrepancy vgchartz numbers seem to be accurate.
and i think i remember Capcom saying something about selling 5 mil copies of DmC. i'm not sure what they said exactly, but the logical assumption is that they are aiming for a minimum of 2 mil, with 5 mil being the optimistic hope of the developers not the shareholders.
personally i feel that it is possible for this title to be a great success, and i would be very happy to see it do 3+ mil, sending a message that a reboot was the right choice after DMC4.