400k-500k in a 5-6 week period. Sales jumped in the UK thanks to bundles and a price drop. Also that 1 million number was announced before Black Friday, and there was news that both the PS4 and Xbox One sales doubled on that day. Then you factor in December, 400k is doable. 500k is sorta stretching it. Also it doesn't matter if the PS4 was outselling the Xbox One in December.
At the bold, are you assuming that during a 4 month period, which includes launch month, 1 off month, and 2 holiday months, 28 countries would not add 400k-500k sales, when 8 countries back in 2013 with only 2 months did 558k combined?
900k unsold can be attributed to MS thinking that more people would buy the system at launch, and the demand wouldn't fall. Also, we only have word about one DC having ~3k units sitting in the US, and German retailers are having trouble selling the console after Christmas. Those two situations don't tell us what every other country is experiencing. It's actually unlikely that MS would have more than 1 million units unsold, because unlike in 2013, they would know what kind of demand the console has.