It's quite frankly, rather hard for me to imagine a world where Xbox exits the living room with no replacement.
Literally zero competitive CoD players for instance, would ever think of streaming as a viable replacement, and Microsoft now owns CoD. Do you really think that they would just abandon the entire living room CoD base to Sony and be willing to give Sony a 30% cut of every game sale?
If Microsoft does abandon Xbox consoles, the smart way to do it would be to tailor Windows with an Xbox / Living Room interface. It's what they're doing for Steam Decks / competitors, and it would be a massive feature boost for them if they sold consoles that were just PCs and had your steam library and mods etc, and then it would let every PC maker (Asus, Lenovo, etc. etc.) become a console maker.