Also could the Nikon D800 be hacked like the GH2?
Yes, it can be hacked, like anything which has a computer inside.
The correct question is, will it ever be hacked ?
No idea on that one...
What I can tell you is that there is a group of people working on a Nikon D5100 and D7000 hack, at nikonhacker.com
They have managed to decipher the Nikon firmware on those cameras.
They also know what kinf of Fujitsu RISC processor Nikon uses in its Expeed 2 chipset.
They also have a software simulator and debugger of that processor.
Currently they are digging in the (long) firmware code trying to guess which routine is called when they press a button on the camera, which is not easy at all.
They are also trying to find out how the camera peripherals (LCD display, sensor, USB interface, ...) is addressed and accessed. So far the have found a routine which draws letters on the screen.
They also try to find a routine which accesses Flash card, which is essential on order to be able to put their own code into the camera without the risk of irreversible firmware damage when they tweak the in-camera firmware directly.
I think, if they hold on, in two years there might be a hack for the D5100.
How that relates to D800 is unknown.
Martin
Martin