Ray,
While not in that same gear configuration as you, I fully understand what you are describing. I have the 1DsMkII, and its 16+MP do a pretty decent job encroaching MF, but not quite there. My 1DMkII cameras are also still very usable, fast, reliable, etc., but are getting a bit long in the tooth. I have been avoiding the MkIII upgrades, simply because I did not see the value for the cost (swapping out batteries, L-plates, etc., in addition to three bodies, 1DsMkIII and two 1DMkIII bodies to manage my shooting). With the D700, I may be able to cover enough of my higher speed sports stuff at less cost with very good results, and the higher res needs would be met by a MF kit. That leaves the M8 again as a travel/casual fun camera that could be replaced with one of the smaller D700 cameras for that use. The lenses are not going to come close to the Leica and Zeiss stuff I have now for the M8, but I think I could manage, even going to the Zeiss options for the Nikon. Right now, the Canon glass is pretty decent, but the body is just too big to drag around. I thought about the 5D, but just could never get myself there, and still cannot. This D700 looks to be a good potential replacement in several categories for me right now. I could dump the 1DMkII bodies and glass to replace with equivalent Nikon glass, and also dump the 1DsMkII and get into a MF rig. That essentially leaves the M8, and at this point, though I hate thinking about it, it too could be sold to help finance the MF side more.
Have to see what, if anything Canon puts out there for consideration, but at this point, Nikon is looking like it is hitting some nice marks for my needs. I also would like to see Nikon put out some lenses like the Canon 85 f1.2L. The rest of the line-up for me is not too far off (70-200 f2.8, 24-70 f2.8, 400 f2.8, etc., though I still think Canon's stuff is better and cheaper than Nikon's on these.)
LJ