Epic Games presents the Unreal Engine 4 elemental tech demo and Engadget had an interview with senior technical artist Alan Willards about next-gen consoles. You can read it over here. The tech demo which you can see below ran on current high-end PC hardware.
"Moore's Law is a great baseline," explains Willard. "You can just rely on things to double every couple of years or so. Some of it extrapolation, some of it is watching the wind blow and seeing that the costs of processors are dropping greatly. And we see whether NVIDA is going to have something ready in time for [console makers] to start developing new hardware. It's strategic decision, and all of development is guess work at some point. But a lot of it experience with the industry and knowing how strategic decisions are made -- not only internally, but how other companies make them, and trying to follow that."