I remember reading a translated interview from Yoshi-P saying that he was thinking of making the game run at 30FPS regardless, but I don't know if that context was being used in terms of the PS3 or not. I know on my PC I can definitely tell the difference between 60FPS and 30FPS.

I think I know what you're asking for OP, to kind of throttle the game when it's in the background, probably for power consumption reduction. It's an interesting idea, I just don't know if it's something they're going to implement. With the new graphics engine in ARR, there should already be a lot less stress on your video card since it should run way more optimally than the engine from 1.0.