4S=5 meaning... I think we'll see one new iPhone this year, and it'll be a combination of what we all think the 4S and 5 will be. The internals of this new phone will be upgraded to A5 chip, 8 MP camera, and maybe more RAM (rumored properties of the "4S") but it will not be in the body of the iPhone 4; it'll be in the body of a slightly redesigned phone (which is a rumored property of the "5" but without the supposedly major internal upgrades). This would explain the new case leaks, which seem fairly credible.
So the new iPhone, which will be called "iPhone 5" will really just be the features of 4S and 5 together in one. There never was meant to be a separate "4S" phone. I believe the "4S" is just a byproduct of internal Apple testing of new specs purposefully hidden for secrecy reasons in the body of an iPh4.
I also think the current iPhone 4 might get a slight spec bump, but retain its "4" name. This will sell alongside the new 5.
Hope that clarifies my theory.
That would pretty much just be a 5 then.
We'll see either a 4S or a 5 but not both. I believe we will see a 4S, then follow the tradition of the 4 being offered at rock-bottom prices. Otherwise the lineup gets too crowded and there's too much blurring of the specs, very un-Apple-like.