People forget that the Xbox one could not create momentum like the 360 did, between late 2007 and 2009 + Kinect in 2010.
The Series S / X will be a tough one to analyze as we don't yet know the impact the Series S/XGP will have on casual / mainstream players.
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They have games + BIG IP that can create momentum, Starfield / Fallout / TES if they are XBOX/PC only, + the release rate that the XGS will have.
Halo Infinite MP too, if it is a success on PC, it will create a big hype on the console market (F2P). From February we will have a more detailed response when stocks will increasingly meet demand.
But I believe the Series S/X will sell lot more than Xone. (70M if they deliver excellent games constantly)