Can they, yes. Will they, Microsoft more likely than not, Sony maybe, and for shits and giggles Nintendo probably. All 3 console makers are probably going to simply use upgraded versions of their current architectures as opposed to older consoles where tech could be drastically different between generations. From a technical point there's probably nothing stopping backwards compatibility just like when you upgrade from a launch PS4 to the pro but whether or not everyone is consumer friendly enough to do it is a different question