Sony has already started R&D on the PS5

[Conina]

"next generation gaming system"... could also be a new handheld or other mobile devices.

Preferred:
•    Current and next-gen game console experience is desirable (e.g. PS3, PSP, X-box 360 etc.)
•    Experience with Unity, multiple player game, networking

They include PSP experience as well as experience with the Unity engine, which is more important for smaller and mobile games than for high end hardware.