4S is probably not long for this world. Right now, its filling a gap both in the product shelf (free) and in an amortization-of-development-costs schedule somewhere. Plus, it allows for some extra profit taking from the 5C for the moment as people eschew the 4S.

I'll bet as 5C production ramps, the 4S goes away in X months. Its in Apple's long term best interests to get everyone on the same screen anyway...