If they replace the 1D IV next year I'm selling all my Canon junk, buying Nikon and turning into the most disgusting Nikon fanboi - anti-Canon-troll the interwebs has ever seen.
Why? Do you think that the 1D MK IV will stop working or making money for you? Cameras get upgraded all the time.
No, but you do understand that this gear represent a certain investment and you don't invested in S___ like this without having some clear idea of depreciation and factoring in the loss in ones accountancy. That is what I'm concerned about, not the camera magically not making me money anymore. Canon has been very steady in update frequency since the 1D.
About the FF debate, meh, don't care, as long as the speed is the same and the pickles stay around where they are now, larger files means more time.
A camera body is not a investment, its a expense. It will never appreciate in value, and after 3 years will drop to 1/3 or less of its new value. My bookkeeper writes off the purchase of a camera body immediately, as he should. A lens, however, may last for 10 years, even more.