I strongly suspect that if/when Xbox outsells PS5, Microsoft is all of a sudden going to reverse their "numbers don't matter" policy, and it'll be Sony that'll claim actual console sales don't matter.
In other words, there's no need to speculate -- we'll know if/when the inflection point comes.
Besides, console sales isn't the fight anymore, based on current trends. Microsoft and Sony are going different ways, with Microsoft going all-in on services, while Sony is continuing it's traditional hardware route. I wouldn't be surprised if this is the last "pure" Xbox generation -- that the Xbox of the late 2020s is actually some sort of Surface laptop / gaming hybrid, if they continue to attach the Xbox name to hardware at all. Game Pass is where the future is for Microsoft, as bad as that is for developers and consumers in the long run (but that's a different rant.)
But if you want Hot Take, no real evidence, predictions, here's one: By the latter half of the 2020s, Microsoft and Sony work out a revenue sharing deal where Microsoft Game Pass is available on the Sony Playstation, and Sony gives up on exclusive first-party game development altogether to focus on hardware development.