If GamePass wasn't available on Windows, you might be right. But it's highly unlikely Xbox will catch up to PlayStation outside of the USA or North America.
But there will be millions of GamePass subscribers now and in the future who don't purchase an Xbox.
Xbox's best market, the United States, still puts it in heavy competition with PlayStation and Nintendo. Xbox is pretty much a nonfactor in Japan, and I don't think that will ever change.
Honestly, Xbox has only a few options if they have any hope of catching up to the PS5 (let alone surpassing it).
-Some true exclusives, either timed or permanent. While a lot of PlayStation titles will be on PS4 or Windows, they have an edge in this department. There's even a third-party game, Final Fantasy XVI, which is only confirmed for PS5. Now I can all but guarantee it will make its way to Windows and possibly Xbox Series S/X. But that will take months or years. Every Xbox Series game right now is available on Windows or something else.
-Massive price cuts, though this would lead to more hardware revenue losses. If Microsoft got the Series S down to $200 and the Series X down to $400, this could undercut Sony big-time. But it would have to involve Sony not dropping their prices as well.
-Bad PR from Sony. They already have some bad PR moves in recent times. But if it got a lot worse, Microsoft could use this to their advantage. Xbox One's bad PR certainly hurt its chances against the PS4. Though In North America, it wasn't as much behind PS4 as you would think.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 48 million (was 60 million, then 67 million, then 57 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima