Wouldn't emulation still be possible though despite that?
A modern powerful computer still struggles to emulate the PS2 perfectly.
A PS3 emulation would have an abysmal FPS, sound tearing and graphic problems.
I think what it comes down to is that building good emulation software is a significant time and money investment for a company like Sony or Microsoft that doesn't provide much of a return for them.
On the other hand, Sony has made claims of using their Gaikai service to allow you to stream and play PS1/2/3 games on PS4 sometime during its lifespan, so in THEORY those games will be accessible. The details, of course, are still unknown.
Also can we hurry up and get PS2 classics on Vita pls