While I know it's necessary to have the bottom unit for output in 10bit 4K I think the GH4 camera is a great upgrade for many of us who don't mind the operational structure of the GH3 but who want more performance at 1080p. And want focus peaking. And the new depth AF. And zebras in camera. And the new faster shutter. And the new higher sync speed, etc. etc. etc.
If the camera hits a similar price point to that at which the GH3 launched I'll add two of them off the bat for my video work and I won't care about 4K until my clients start asking for it.
This is already a much, much better value proposition than anything Canon has out and is so much better operationally than anything Black Magic offers.