Looking how some emulators just ask users to copy firmware / software / keys from their real consoles - couldn't the same thing be done and only the hardware layer be emulated?

How do you get that software out of your console ?

rpcs3 just uses the PS3s update pup files to install the OS so I imagine there might be a way for newer consoles like that. You can obtain the PS3 ones directly from Sony for use on a flash drive to update the console.

No idea, that's why I'm asking :)

I guess there may be ways to do it not really legally by some hacker and then sharing it with others.

Not that I support it, but there are still people who don't see problems with such behavior.