Honestly, I would avoid the mk3 right now. If a new one comes out at photokina, then you'll take a huge depreciation hit right away, and probably regret the decision. Even worse, it will always have a stigma - which will kill your resale value as well.
If you really HAVE to get a new camera now, then look into a 1dm2 for half the money. If a new mk3n comes out, you'll probably still be able to resell it for a minimal loss (it's already taken most of its depreciation). Even better, it's a great camera that is RELIABLE to the core. It's only sin is the smaller lcd
Current: 5DM3, 6D, 8mm fish, 24-105/4IS, 35/2IS, 70-200/2.8IS, 85/1.8, 100-400/IS v1, lensbaby composer with edge 80, 580's and AB800's
Formerly: 80D, 7D, 300D, 5D, 5DM2, 20D, 50D, 1DM2, 17-55IS, 24-70/2.8, 28-135IS, 40/2.8, 50/1.8, 50/1.4, 70-200/4IS, 70-300IS, 70-200/2.8, 100 macro, 400/5.6, tammy 17-50 and 28-75, sigma 50 macro & 100-300