But they can accomplish the exact same thing with a PS4 Portable, have more demand, higher profit margins, and have a design that can be applied to high-end mobile phones at or after launch to maximize returns on the APU.
For whatever reason Sony are just very bearish on doing 1P AA content; those kind of games would not require scoping, dev time or graphics fidelity of the AAA 1P games and could scale very easily to a portable of PS4-level spec (in terms of TF; an actual PS4 Portable would have higher pixel fillrate, texture fillrate, better GPU data compression, cache scrubbers, audio engine and support for more modern graphics features).