Firstly, throwing money into first party games and releasing them on all systems kinda invalidates the "software licensing" part that forms the basis of your point. They'd be giving that licensing fee to the other platform holders instead. I'd also imagine that incremental hardware revisions wouldn't have the same design and production costs as the entirely new architectures we've been seeing across previous generations.
As for cross-gen forever... logically this would already be the case on PCs if such an assertion were to be true.. but it never has been. Rather than "lowest common denominator" it's pretty much always been a case of "lowest common reasonable denominator" which general tend to be what the general console generation is, or in the absence of that (such as the iPhone) something like every other cycle.
