I'm in a dilemma as well. I am definitely getting a 5Diii, but am thinking about selling my mark ii in order to purchase a D800e. Half my work is weddings, half is landscape photography. Then I would buy a 14-24 and maybe a few primes to start out, while keeping all my canon lenses. Apart from the question of money, I don't know if it's wise. Because for weddings my wide, backup body would be a Nikon. I can't imagine not swearing every time I switch from one camera to the other because buttons and switches are in completely different places. I can guess that no one here things that this is a good idea...myself included. But is it worth the benefit which is this: I print 24x36 and larger prints of my landscape photography. I'd like to get more sharpness that I currently do out of my 5Dii for these large prints. Other photographers who I interact with shoot MF. So that's what my stuff compares to.
The biggest reason I think is that I hike and climb for about half my shots. I carry a 5D, TS-E 17mm TS-E 24mm ii. I don't use grads. I take multiple exposures if I need to grad something later. If I went with a D800E, not only would I have extra sharpness, but I would have more DR to work with, thus bracketing less often(I hate bracketing), and no grads necessary. I also could use 1 lens 14-24 and could actually use ND if I needed for long exposures, where the TS-E 17mm it's not possible (without being creative/sketchy).
So I need to decide if it's worth the trade-off, or maybe just save up a little so I can keep my 5Dii as a 2nd wedding camera.
What would also help me to decide if it's worth spending all that money on new lens and camera is a real life side-by-side test. I'd like to see some high dynamic range landscape scenes shot with 5Diii and TS-E 17mm and TS-E 24mm, then side-by-side with D800E with 14-24 at same focal lengths.
So if anyone who have both on hold, and own these lenses, when you get the cameras, you should do a side-by-side comparison for the sake of us landscape large-printing photographers.