How certain is it that PS5 won't be backwards compatible beyond PS4?

[Excalibur]

I would very much love for an all in one PlayStation, that would play every game released on a PlayStation console, But I've learned not to get too excited about these things, PS4 BC was expected, with the PS5, same architecture and all, so i wasn't too surprised to have heard that and there was that patent some time ago that seems to imply the other older PlayStation consoles could be BC as well,  but it's still not a confirmation, there are many patents that never materialize, so i will remain skeptical until we know one way or the other for sure.