Not putting a wager. Just going to say 11.5 million. It will get a boost this holiday and next year with Halo.

So far, it doesn't seem to have changed much from the results of the 2020 vote.

8M-10M.

Relatively strong launch, for good enough reasons, but I'm guessing sales decline slightly in year 2. I'm thinking the hardcore XB fans already got one.
For the semi hardcore XBSX hunters who didn't, they'll get theirs next year, but I'm guessing that by the holidays, the XBSX won't be sold out anymore.
I'm also gambling that shortages will be relieved enough by holidays next year, that relatively more available PS5's will lead to a slight XBSS decline.
I'm thinking best case scenario next year is the same sales as this year.

I'll go with around 10m. Stuff like Starfield should help keep demand high but it will mostly come down to how much Microsoft can ship.

I checked on ebay to see how many new (not used) consoles were sold.

December 3

PS5 507 units

Series S 30 units

Series X 232 units

Xbox demand should be very high right now thanks to Halo infinite, but it's still about half of ps5.

As every console offered is sold - doesn't that just mean more people sell their PS5 than their Series X?

MS must have had a lot of Xbox ready for the launch of Halo Infinite.

Did you not expect a lot of Xbox to be sold in December ?

On ebay?

If the supply of Xbox increases, the amount sold on eBay will also increase. Anyone can sell there.

I was checking eBay in the fall as well, and one thing that has changed is that the bidding prices for Xboxes seem to have gone up quite a bit. It is now selling for the same price as the PS5.