What's with all this speculation on what GPUs it needs? We don't even have a leaked beta, geez.
For all we know it could need TriSLI GTX580s to play on medium, or it could be the same as BC2.
Now, if i had to guess, this game would be a VRAM and CPU bottlenecked. I'd expect the 6970 to shine over the GTX580 at 1080P. again, just a guess.
It doesn't seem to look more demanding on actual GPU power, but the textures and explosions may bottleneck.