I did not plan to wait for a Mark III, and had started making some sacrifices to enable purchasing a 5D Mark II, or perhaps a Nikon D700, but then I had an opportunity to purchase a very clean pre-owned 7D, and went for that, instead, which actually means I now have two 7D bodies.
Well, I did the math, and found that what I paid for the pre-owned 7D, plus where some original 5D cameras are currently priced, is comparable to what a new Mark II costs, so I am actually considering an original 5D, to finally be able to try full-frame for portraits and landscapes, primarily with a tripod, when weather-sealing, fast handling, and fast focusing are less important.
To be clear, I am not recommending that anyone settle for an original 5D, just offering my view on obsolescence. A well-maintained product still does what it did when it was state of the art, so the introduction of a newer model does not make its predecessor obsolete, if the manufacturer (or aftermarket) is still supporting it. If a 5D Mark II does what you need it to do, why wait for its successor?
Moreover, with the epic tsunami of 2011, the wait for a successor may be long.
Canon 5Ds R/7D2/7D/5D/40D/1D2N/M3; Nikon F6/D3s/D700/FM3A/1Dx/Coolpix A. Lens selection undergoing changes; some favorites: Zeiss 2/135 APO Sonnar, Canon 100mm f/2.8L Macro IS and 135L, Nikkor 14-24/2.8G and 24-70/2.8G.