Thought I'd post this, since there is a lot of misinformation online about this subject.
You can hack GH4 .rw2 files to be editable in both LR and ACR with a simple exiftool.exe trick.
For PC's, download exiftool.exe. Be careful to get it from a reliable source, check it with Norton, etc. Can't remember where I got mine. Put exiftool.exe on your desktop, or anywhere you can remember. Exiftool.exe doesn't require a formal installation, you simply put the file in some directory such as the desktop.
Load the PC Command Line dialogue (remember DOS?). There's something similar in the Mac OS, I think.
At the command line prompt, type:
exiftool.exe -model="DMC-GH3" -overwrite_original c:\gh4\folder01\*.rw2
If everything works OK, you will be told how many files were converted. If you are told "file not found" it probably means the system can't find exiftool, or there's a typo.
I'm sure you can figure out the path statements. "c:\gh4\folder01" is on my system, but your folder may be named differently. Remember that exiftool itself must have a path specified, or exiftool.exe must be within the current directory, which is why I did the "desktop" thing.
So now LR and ACR will think those are GH3 files and will load and process them quite well. OK, so there are probably some subtle things that will be different in the officially supported versons, but right now you can edit those .rw2's to about 27 times the quality of a jpg.
OH, did I say back up your original GH4 .rw2's? There is no free lunch. Theoretically you could later use exiftool to set the model name back to DMC-GH4, but I don't know if LR or ACR make their own changes to the raw files that would later conflict with that, or if there would be .xmp file issues.