If they're putting PS1 and PS2 games on Gaikai like they said, they're coding an emulator for a PC architecture. Same with the classics on PSN. Hell, Sony coded a PS2 emulator that runs on all PS3s just for a couple dozen PS2 Classics on PSN.Well, there is also the hurdle of, I don't know... coding the emulator?
Yeah, the PS4 probably has enough power to emulate PS2, but the effort needs to be put into the software for it. Emulators are not trivial tasks, simple as that.
I still have hopes that they release some sort of "add-on" for this stuff. I remember a Sony patent from a couple years ago that was about a small USB add-on that would have something like the partial hardware that the PS3 originally had to provide BC.
Now that they finally axed the PS2 production, I would hope something like this comes out.