I agree, you'll never get one camera that does it all (hence why I've got a collection that's growing out of control!) but, a broadcast "legal" GH3 would be a very unique proposition in its own right. I do a lot of snow sports filming, both action and corporate, and very occasionally have a need to shoot broadcast accepted footage. Lugging several cameras around a mountain isn't really an option so I have to make do with one system. To make matters worse, I shoot both stills and video!
The C300 is probably the closest to a do-it-all at the moment (great image, 50mb/s 4:2:2 codec) but it has no stills capability at all and slow-mo is only at 720p. The FS700 with external recorder does stills but not properly (no raw, no flash etc), it's not weather sealed and, as much as I want to, I just don't like the look of the footage. I really like the footage that I'm seeing from the BMDCC but it's a complete non-started in terms of practicality for me (for starters, I'm not taking my gloves off to use a touch screen when it's minus 20 degress C!). The new F5 does look great but it's going to be too big and heavy, and basically overkill, for most of what I do.
The 5D Mark III that I'm currently using (alongside a couple of GH2s) is supposedly getting a clean 4:2:2 HDMI out in March but the resolution is still going to be the mushy 720p-esque stuff that we have at the moment.
I know that my requirements are very specific but, for me, a GH3 with the option of occasionally using an external recorder for broadcast accepted footage, rather than using an entirely different camera, is pretty attractive!
So, if anyone knows whether it's going to be 4:2:0 or 4:2:2, I'm keen to hear!