This.Kumagawa Misogi said:PS1 mips cpu
PS2 mips cpu (backwards compatibility with PS1 super easy)
PS3 Power cpu (backwards compatibility only possible with PS2 with PS2 cpu included result increased cost = complaints of it's too expensive so it's dropped and sales increase).
PS4 X86 cpu (same as with PS3-PS2 only possible with additional hardware and increase in cost so they don't bother as people complaining on the internet does not effect sales cost does
The huge effort required to build a software compatibility layer to translate to a different architecture is simply not worth the time and money. Embedding a second CPU is too expensive.
An emulator would not run smoothly for PS3 emulation and even PS2 emulation still requires a very decent amount of CPU power. My desktop can run a PS2 emulator fine but my laptop struggles. I would imagine that someone, somewhere will be able to get custom software running on the PS4 and recompile PCSX2 to run on it. Which should be mostly straightforward seeing as it is written for x86. That would give the PS4 backward compatibility with PS1 and PS2 games which is the best anyone could hope for.