I agree with Brian that their "big" camera is a more likely candidate for a refresh, since it's farther along in the development cycle and the GF-1 seems to be selling briskly (it's not even available body-only yet, AFAIK.)
My question is whether they're going to continue to bother having non-video and video models within the "big-camera" subline. I think it would be more logical for them to pare down their Micro Four Thirds lineup to one compact model with "consumer" video features (GF-x) and one larger model with "prosumer" video features (GH-x.)
Under this logic the GH-x model would get refreshed next with the new sensor and whatever other goodies they've got in the back room (e.g. eye-level finder with their new high-res LCD, as on the EP-2's accessory finder, instead of the expensive sequential display) and then the GF-x model would get a corresponding refresh a few months later, and then they'd continue to alternate updates between the two product lines.
I also wonder whether they'd continue calling it GH-2, GH-3, etc., or adopt Nikon's convention of calling it, say, "GH-1s"...