It looks like the Foo's are currently in the studio now doing something album related. I remember they said they wanted to record in Dave's garage and this looks suspiciously like Studio 606 but maybe they are doing the pre-production/demos here for now. Either way calling Butch Vig in for just demos seems a bit suspect.
Here's the photos pulled from the Foo Fighters Facebook feed last night:
It appears it's all being filmed!