It may be heretical in this forum but I was never impressed with the pixel density of the 12MP FX bodies, so I stuck with DX waiting for this camera. Bear in mind, I primarily work from a tripod at base ISO. When I do shoot hand-held, it's for distant subjects like birds, and usually in good light, so I usually don't exceed ISO 800. For me, FX just looked like bigger, heavier lenses, and no definitive advantage.
That said, my DX landscape telephoto is a 70-200 VRII because I knew this camera would come eventually and I was already planning my kit around it. With my 50mm f/1.8D, I'm adding just a Tokina 17-35 f/4 and I have a complete FX landscape kit. That 35-70mm gap is not a concern since I rarely shoot there anyway and 50mm should cover it. For those times when I want to "walk around" with a general purpose zoom, I'm not looking for super high-quality images and happy to use DX for that.
So, I will sell my D7K once D800 arrives. I'm keeping D300s for its 7fps for shooting birds, and since I usually crop DX bird pics anyway, no advantage for FX. It's tempting to keep the D7K, especially since it uses the same battery as D800, and gives me a lightweight body option, but I'd miss the speed too much.