gh2/3, and really m4/3 in general, was never really intended for the pro photographer. until the gh3, panny never really incorporated 'pro-user' features; or at least advertised them as such. the gh series just happened to have some really good video output, and then only made better by vitaly and others. if you look at how these cameras were/are marketed, the intended segments aren't the pro photographer, let alone filmmaker...the users made them as such.
i don't think it would make sense for canon to make a specific 'gh3 killer,' because if you look at the buyers of these cameras, i'd say the indie filmmaker is actually a fairly small percentage. canon wouldn't make a full frame, top of the line 'pro model' dslr, and then cram it full of top of the line 'pro model' cinema eos stuff as well. people shooting dedicated stills don't need 4:2:2 color, 4k or any of the lauded video features; and people shooting dedicated video may not want the dslr form factor, rolling shutter issues or so on. it reminds me of the 'old' car saying, 'fast, cheap, reliable...pick 2.' there is no such thing as the 'perfect' all-in-one; in cameras or otherwise, because it has to be good at everything, it doesn't excel at anything.
if you already haven't bought into a canon/nikon system, (someone like me) m4/3 is at a more affordable price point for lenses (legacy lenses). there are drawbacks with crop factor, manual focus and so on, but i rarely use autofocus, even for stills, and i really haven't had any issues with the 14mm end of the kit lens not being wide enough. so for me, and i think many others, the benefits of a great video camera, pretty decent stills camera, a bunch of adaptable, fairly affordable, lenses, smaller form factor and other little details (audio levels, histogram, pretty much no moire, etc) and then the pricing of the cameras themselves, brought them to their purchasing decision. i believe canon will remain top of the camera makers, for a while. but these kind of oddball cameras like the gh series are doing enough to cause the big guys pay attention