Matt has said on the ResetEra thread that this number does not count bundles and that it is in terms of $$$ not units.
Pretty amazing since all the other big super-hero games (read: Arkham) are multi-platform.
Pretty impressive then. So with bundles counted, maybe more than 5 million in USA by the end of the year?
Very good news about gaming sales everywhere right now, well maybe except for BFV and F76...