"Buy GH4 or wait... for what?" This is interesting question.

When I saw a 4K 50 inch TV set in the stores in shopping mall I did a close look to see the pixels. I put my eyes as close as I could before loose focus and it was very difficult to see the pixels. In fullhd TV sets I can see the pixels from some distance and this makes me want 4K which I perceived to be pretty enough improvement from 1080p.

If you start to consider the viewing distance from screen, the fullhd 1080p tv set needs to be away around 2x the screen width from your eyes to avoid seeing the pixels, and 4k tv needs to be away 1x the screen width from your eyes to avoid seeing the pixels. If you sit in from a tv or a projected image at a distance equal to the image width it will be too much near, not so comfortable to watch, so 4k is enough resolution.

these two things makes me to perceive that 4k is pretty enough resolution for tv, home projectors and also for cinema theaters. the 8k image is a japanese luxury to make the image to become real life in front of you when you are very close to the screen. imagine a powerfull computer to edit a 33 megapixel video, 7680 x 4320 pixels!!! Preview effects will be hard, rendering times will be looonnggg!!! the resolution is more than audience need.

So GH4 with excellent 4K video is a great camera. sony A7R II with internal 4K recording is also amazing for people who likes full frame sensor, full frame lenses and low light, A7S II will be even better if it can do a full sensor readout in 4k fullframe.

Ok, 4k resolution is more than enough... so wait for what???

There are three things I would like to see in GH4 successor: first less noise in high iso for a better low light performance (difficult to do in small m43 sensor, so sony full frame mirrorless can be better choice for this), second more fstops in dynamic range using two exposures merged in camera like the a7000 rumors are saying, like the organic sensor is saying, like the nikon honeycomb sensor is saying, but this will take some time to be real and even more time to be real and good quality. Third thing is 4k at 60fps for slowmotion to avoid using lower resolution in slowmotion, in 1080p cameras only 720p could do 60fps, now the 4k cameras can do 60fps in 1080p, in near future the 4k cameras will do 60fps in 4k. V-log seems to be a firmware upgrade for GH4, but to be honest I do not like to keep doing difficult image grading in post, I think Cinelike profile image is good dynamic range and more easy to work with in post. Multiaspect sensor would be welcome to make the 4k recording using a large m43 sensor as GH2 can do for less crop in lenses.

So my desires are: 4k @ 60fps, hdr video with two exposures merged in camera in 4k, better low light performance, multiaspect sensor with 21,6mm diagonal in 4k, all the diagonal that m43 lenses can do. And just one more thing is the 5 axis stabilization in the sensor in the camera body same as sony A7R II. I believe there will be an interesting battle between sony mirrorless and panasonic mirrorless from now...

I forgot to say: why not increase the datarate in 4k? would be very good to have AVCHD 4K with intraframe compression and 5:1 compression ratio which is ok to avoid all artifacts and mud like the The End NR4 patch can do for GH2 in 1080p. I think this is a dream which will not become true, but a little more datarate than GH4 would be welcome for 4k... And I would like the future 4k cameras to keep recording in AVCHD because it is more easy to edit without transcoding the files, HEVC H265 is hard for computer to decode and I woul not like to do computer upgrade or files transcoding all the time...

I have the GH4 and A7s

That said, I only use the A7s in poor/low light Video. 1. This camera absolutely needs a 4k recorder. I have the Odyssey 7Q+. It DownRes 4k to 1080P30. Even using ProRes LT the results easily beat anything I can get when recorded internally. 2. The A7s needs an external battery to record much more than the 29 minute internal limit. 3. The A7s needs a Cine lens to work best (although I get good results from my Pro Nikkors). I use the 28-135. 4. I run this camera with fixed ISO and often manual everything. 5. This camera requires a good TriPod and Video head. 4. My total cost is close to $8,000+

I use the GH4 for everything else. 1. The internal codecs are so good, I think an external recorder is a waste of money. 2. I can record internally 3 hours non stop on one battery. 3. The AutoFocus and AutoISO are good enough to run this camera unattended. 4. I only need one lens. The 12-35 covers the range I need and I can use the 35-100 for Equestrian Events. I bought a generic SpeedBooster after trying the MetaBones but have not used it since getting the A7s. 5. I have used this camera hand held for Video and Stills. Not easy but possible. 6. The entire kit fits in my smallest bag. 7. Total cost close to $2,600 not including second lens

Get the gh4.

I've had terrible luck with JVC cameras. Just one guy, but as John Lennon said, "I'm not the only one..."

@ipcmir It's a point that I've not really used the BMPCC in low light but I just love the look compared to the GH4.

The next big things is going to be really big as far as things go.

The best camera for my use has not been made yet. I am waiting for the CamCorder with A7s sensor. I use my A7s indoors in poor/low light. Way too low for my GH4. But I also want the controls of a Pro CamCorder.

If you are willing to wait, I see no reason that Panasonic can not double the usable ISO on the GH4 when they release the GH5. It needs to be at least 6400 clean for me to "upgrade". And, Panasonic may finally release the successor to the AF100 CamCorder by next Spring.

The new organic sensor may be ready by next year. If so, I expect to be amazed. 12MP would be enough for me if optimized for 4k Video.

Nor an organic sensor in a camera next year :(