The Magic Lantern hack is not really a hack, it is extremely stable, but it does not do 4K it only lets you shoot RAW video, and also gives you 300% optical zoom in RAW
Full frame cameras any day for taking stills, I have a GH2 and a 5D MK3 and I can not stand taking stills on the GH2, although it is great for video.
If you want to have larger prints, you may consider the A7R (36.4 MP)
The 5D MK3 does seem to be coming down in price lately, and there are rumours of a larger MP Canon camera on the horizon.
I believe the GH4K will be announced tomorrow.
There has been rumours of an 80MP Canon EOS 1D for the past 8 months, who knows regarding that, but expect to pay a LOT more for that if it ever materialised.
Canon has a lot more good glass than most of the others, and always pay well for the glass as it will be with you for a lifetime, and Canon stuff can usually be used on many other cameras.
If you are going to go down the RAW root for video think of buying a new PC that will also cost >$2k
Just all depends what you want to lift, its a good time for cameras and Im sure we will see lots more changes in the coming months, if you want something cheap and really light check out the panasonic GM1, same sensor as the GH4 and cheap as chips.