One thing to take into account, is that Sony won't allow MS to thrive where PS can easily as well, and that's with hardware.
If XB Series S is really doing that well for MS and continues to, then you can bet Sony will do something similar next gen.
If for whatever reason next gen, Sony can't guarantee vastly increased chip production, they'll just copy the low end model.
The difference will end up much like Pro vs XB1X. Sony's low end launch model will be slightly weaker and $50-$100 cheaper.
Which will almost certainly mean a high end PS6, like the PS5, slightly weaker but same price as high end XB Series 2 X.
So something like a $250 PS6 S and a $500 PS6. (why not a $750 PS6 BC model with built in Cell BE while they're at it?)
Game Pass or not, a $250 next gen PS console vs a $300 next gen XB console will likely end up a big win for Sony.
That will probably mean the high end PS6 model won't shine like it could, but will allow the market share to shift considerably back to PS.
If that was the same market, I'd agree with you. But by next gen the market will fully be feeling the impact of Microsoft scooping up so many formerly multiplatform developers and either turning their games into exclusives or making it seem like a no brainer to play them on their devices due to how much you save with Gamepass.
PS5 is still going to get a lot of games due to existing contracts. But PS6 isn't going to get Elder Scrolls 7, Starfield 2, Fallout 6, Doom 4, Call of Duty, Diablo 5, Overwatch 3, or the endless list of other games they would have gotten access to just a couple of years ago. PlayStation is internally bleeding, but because it isn't visible on the outside its fans are thinking they are healthy. By next gen, there will be visible signs.
Most PS fans see it. It's why Sony was pushing internal growth prior and why more recently they're pushing larger (strategic) acquisitions.
Sony won't just let MS gobble up everything. If it's going to become a game of exclusives again, clearly this time, then Sony will buy what they can for now and make it exclusive, when need be, in kind, to keep you in their camp.
Then the next hope, or plan, seemingly anyway from Sony, would be that some their new in house IP, campaign, live service, etc, will please those existing, new or XB gamers, and bring them into the PS ecosystem. Why get XB for COD if PS now has it's own competitor and is considered worthy?
How many casual consumers really sit down and think long term as to how much Game Pass would save them in the long run? Most will see a cheaper PS6 S and will buy it, just like XB Series S. Game Pass is just an extra cheap bonus on top right now since there is no alternative.
If they start looking at services, Plus offers a ton of games and is cheaper in yearly form. How many casuals will really require day 1 to be a must when purchasing a console for a service in mind?
There's no longer sunk costs either. There's no reason not to jump from XB Series S to a PS6 S, because you don't own any games from Game Pass.