As much as I like(d) Sega, they were never the champ. Even at the height of their popularity, the Genesis was still a somewhat distant second behind SNES. After that were multiple generations of floundering until eventually they fizzled out (and I say that as someone who likes the Dreamcast far more than any Sony console). Meanwhile, Sony has maintained high sales the entire time. Not PS2 levels, mind you, but still high worldwide, with the Vita being the only exception. They only major region they’re dropping off is Japan, and Microsoft has gotten by just fine without them.
I think my ideal realistic scenario is that Sony rides out this generation, but they use this time to experiment with putting their games on PC, eventually deciding to follow Microsoft’s lead and put all their games on PC in addition to their own console. They then decide not to make a PS6 while also keeping the PS5 on life support for as long as possible, as they tend to do with their systems. I could see it being alive - as in, “getting new releases” - for at least five more years if they play their cards right.
My ideal unrealistic scenario is that the PS5 crashes and burns and Sony goes third party ASAP because fuck ‘em and their ravenous fanboys. Then Nintendo goes PC because I’m tired of their otherwise great games being held back by stupidly weak hardware. Then Valve keeps getting better at making hardware and improving Steam OS to the point where it becomes as stable and user-friendly as a console. Then Microsoft… can just keep doing what they’re doing, I guess.