Some useful information - thanks. Of course I forgot about GX7 - that's got a lot going for it. Couple of other considerations are that I once had an Olympus 8080; if their menus haven't progressed a lot since then that would definitely put me off. And yes the zooms put a ceiling on ultimate performance so perhaps my most important requirement is to keep the feature set of the GH2 with better noise performance. Thinking about it, the format change is something I use a lot; obviously you can crop later but then you lose a bit of sensor area. So maybe I should stick with the GH2 and concentrate on optimal techniques for noise reduction because "jack of all trades" to me includes low light use (of course indoors the GH2/20mm is a nice discrete combination).
Its a tough one.
I'm lucky as I have a number of MFT cameras, so I tend to pick the one best for a particular job. I often do paid work which requires a totally silent camera in often low light, I used a G5 for a while to do this (which is pretty much the same sensor as the GH2) but now I have the GH3, this tends to get used just because it gives a little bit of extra headroom at the high ISOs. I say little because I tend to limit myself to ISO1600 with either camera. I suspect if I needed to go to 3200 or 6400, then a GH3/EM5 type would indeed start to be far preferable and it wouldn't then be a 'little bit' extra.
However for landscape work at base ISO, well .... really ..... while the newer sensors might indeed have cleaner shadows, what I find is that if you're pulling the files THAT much so that you start to notice the difference between a GH2 and a GH3, to be honest, other aspects of the image start going to $hit anyway, and if I knew that I needed to do some severe PP work on the final file, I'll probably have done a 5 stage bracket anyway, and then any difference disappears.
Worth mentioning that in the UK anyway at the moment, Panasonic are doing some really interesting deals, where you buy a GH3 body, then they give you a grip, battery, and a 25/1.4 pannyleica lens free. If you wanted those things in the first place, the body is almost free!
I don't see the GH3 as being particularly big myself, as I tend to have a lot of lenses, so then the system size as a whole is dictated by these, not the body.
If you haven't tried a GH3 in person though, I recommend you do first if you were considering one, as many people (myself included) consider the viewfinder to be really dreadful. Awful colour reproduction (greens especially) and blurry edges if you move your eye at all from dead centre. Different people seem to be affected different amounts by this. Some claim they can't see anything wrong. Drives me insane. Doesn't affect the final pictures of course
I have been on the fence about buying a GX7 to replace my EM5 for a while. Still might do it as there is lots about the Oly that bugs the hell out of me, and the shutter shake is often a huge issue, but the IBIS is excellent and it often lets me take excellent pictures hand held with some older 4/3 lenses I have. However I tested the GX7 IBIS as well and while I didn't like the fact that it doesn't stabilise the viewfinder when you half press the shutter, the actual stabilisation itself worked far better than I'd expected. If small and better high ISO is something you're after, I would look at the GX7 seriously.