Not what I said. I said many people will be BUYING both, not OWNING both (and there is a gigantic difference).
For example: I have bought every model iPhone. I only own 3 now (my original 2G and a brand new 4S for nostalgia...) my 5S being my primary device.
I agree that not many people will OWN both, but because we live in a society where "most" people want the latest and greatest (and will line up by the millions to get it on launch day), why is it so hard to fathom that people will buy the 4.7, and then get tempted into "upgrading" to the 5.5 in a few months because of the Sapphire screen, or whatever other goodies they include???
They will, and even though you may not, I probably will too. If the 5.5 isn't worth it, no biggie, I'll stick with my 4.7. But if it is, I can either SELL or replace my wife's phone with the "old" 4.7, and get my shiny new 5.5.
And yes, for the poor folks that have 1 contract and no money that would never happen, but there are PLENTY of people that don't fall into that category that Apple can use to their benefit by staggering the release.
It WILL happen. Maybe not for you, but it will.
But no, I don't recall saying people would be using both devices at the same time... just buying both (and selling/finding a new home for one, of course).
Apple doesn't care (for the most part) what you do AFTER you buy it. If you sell it right after you buy it to buy something else, they still count it as a sale to their shareholders. They just want you to BUY it in the first place

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