Modern engines are quite scalable, and their mid to low settings can run even on hardware as old as current gen (2006) console hardware.
Hopefully, the rumors about APUs being used aren't true, as that kind of hardware is mainly suitable for HTPC usage, or non-interactive content. In any case, most developers agree that the main purpose of the next gen consoles is to bring 1080p running at 60fps, but it's all but certain that photorealistic textures and gobs of shaders are going to be used, saturate bandwidth and get back to struggling to even reach 30fps, just like the current gen does.