http://daringfireball.net/2011/09/teardrop_skepticism
And he goes on to talk about the iPhone 4s and the iPhone 5. Apple, as usual, keeps everyone on the edge of their seats.
My personal take is that Apple should just do the iPhone 4s. In head to head sales, the iPhone 4 still kills everyone else. I'd let it get a little staler -- and then drop the iPhone 5 say in June of next year.
They can do the tick-tock, like Intel. One year, new design, next year use better components. And they can have the iPad and iPhone tick/tock on opposing years.