As I see it is not so much about RAW sells numbers, but rather a matter of sustainability.
Console releases are always a disaster for hardware manufactures, because they take even a longer time to develop than games, and the gamble is far greater. This gen have been more accessible then the previous gen (PS3 being launched at 400 USD instead of 600 USD making room for better competition and all that), but problem for MS is Kinect, and dropping it will really have a hit on how the company will profit from it.
Now, the sales figures are very shady, as what is conceived as actual sells rather than retail distribution is really complicated to determine something doing good sells vs bad sells, distribution to retailers are not sales per same but stock demand, if they run out of stock they will ask for more, if they don't they might just keep what they have in store, thus negating further purchases and see a sells trend drop.
MS can keep a sale store record, retailers will ask for new X1 units to store, then a time will pass and for some time we'll see how much retailers will ask for restoring units, depending on that trend we will see how well the X1 sells. The introduction of new markets broaden this as retailers will have the X1 in stock for the first time, thus seeing a boost in world wide sales.
Now, the problem with MS is that they got basically 🤬 with the Kinect, the dev time and the production of the device will not be returned as the unit production is far more costly and the targets were not met (bare in mind that Sony had enough resources to Produce 7 million consoles and supply them, which is a huge investment for them, something that made them loose revenue Q1 this year apart from selling it's PC division and so on), if MS had projected an scenario in which new subscribers+units sold will make up for what the dev costs then is really problematic for them, hence why they dropped the Kinect and are trying as hard as they can to make revenue while staying competitive, parting from expecting around 7 million sold they devoted resources to production of such number of units, resources that will not see as much revenue as they should.
Buying a PS4 at release makes me biased, seeing the same X1 boxes at local retailers is another story. Local retailers don't know what to do with it as they can't drop the price of the device to a PS4 competitive price because their revenue would be far too poor, and people more inclined to cheaper products while the PS4 is also advertised as "more powerful" and often bundled with a Vita or a year of Plus which makes both Sony and the retailers win a bit alike. With MS everyone looses as it's not competitive enough to a competitive market.
Kinect and this X1 release will kick MS in the back in a few years down the line as production targets and revenue expectations are not met. Rebuilding the One to work without Kinect will also generate both design and production costs to the already generated cost of developing the console in the first place, just to be competitive in a market that is already devoting some of it's resources to future peripherals (See PS eye integration with Morpheus, is which clear going for a market that only exists in PC and has no competition for the mainstream audience, making it a huge revenue potential in a mainstream market other than establishing yet another additional feature to be even more competitive to MS X1 nerfed unit).