yes, 4K gave one the chance to apply post stabilisation but at the same time it gave one the chance to reframe the shot, get rid of that guy in the fluorescent jacket just at the edge of the frame or correct a horizon. Having a bit of the frame to throw away is always a good thing.
DOPs can obsess about bit rates so having a bit in hand will always help there.
If one's in the market for a new camera then the extra few hundred pounds is not that significant. The GH4 is priced the same as the GH3 was when it was released. Wait a few months and the price will drop, thats when trading up will be more attractive. In the mean time it is worth holding off purchasing a new GH3 and go for a GH4. If you already have a GH3 then don't fret, it's going to serve you well for a long time.
4K is a much better bet on the future than 3D was a year or more ago.
( Has anyone noticed that if you keep the shift key down typing 4K you get $K ? )
andy