Thanks Michael and Larry for the comments.
I'm in exactly the same situation as K Bennett, shooting the GH2 (for stills, not video) and looking at the fork in the road -- a choice between the GH3 and the OM-D. It's further complicated by the presence of the G5, a new camera that is smaller even than the GH2. The G5 has the same Venus processing engine as the GH3, but a different sensor, apparently. I wonder how much difference that makes? It's still rated to 12800, but the camera is about half the cost of the GH3. I wonder how much of that extra cost goes to video capabilities, in which I'm not interested?
I'm also somewhat plagued by reports of the GH3's size -- I value small size, but the GH2 is fine with me. (Besides, when I really want to go small I have two GX1s.) I have not actually found a GH3 to handle, but according to the specs published by DPR, the GH3 is only about .36 of an inch wider,.12 of an inch higher, and .24 of an inch deeper...or a little more than 1/3 of an inch by 1/8 of an inch by 1/4 of an inch. That doesn't seem like very much to me, but as I say, I haven't actually seen one yet.