Nope only be able to use it for physics, not graphics rendering.
R580/580+ and R600 will be so fundamentally different in design as to not work well in CF without serious tweaking to the point of an R600 emulating an R580, which loses most of it's benefits.
It is technically possible to do it, but I doubt it'll ever be supported by ATi as it would cause a ton of driver developement headaches, it could probably be done for a basic 'proof of concept' type of thing but for the general public consider it a no go; kinda the difference between impossible, and impractical/implausible.