Xbox Series X|S should be +3M in shipments. Below XB1's 3.9M but that's expected due to the shortages.
Sell through should be equivalent as well given it's still sold out, and there will always be a few hundred thousand units in transit to stores.
Won bet with t3mporary_126 - I correctly predicted that the Wii U's LTD at the end of 2014 would be closer to 9 million than 10 million. http://gamrconnect.vgchartz.com/post.php?id=6673287