One thing that I'd missed in the big launch of iOS 7 was that the colour palette of the system remakes itself based on the wallpaper that you've selected.
That's interesting in only the smallest of ways in itself but I think it is a good indication that a cheaper iPhone is coming and also of potential features of its design.
As I've said before Apple's reduced profit margins suggest that the mix of its biggest profit maker (the iPhone) is weakening. People are buying cheaper iPhones - the 4 and 4S, which are both still pretty competitive devices.
I believe that Apple will recognise this move into new market areas and deliver a cheaper iPhone to compete with mid range Android and Windows phones whilst making better margins than the older models.
This is where the palette changing optimisation of iOS 7 gets interesting.
The new cheaper iPhone is likely to be plastic and available in a range of colours - coding each device with the colour of its shell would allow iOS 7 to include that in its palette changing algorithms.
But extend it further, why just lock the phone to a single colour. If Apple were to make the shell replaceable with different coloured shells they'd open up a whole new high revenue stream for themselves. Ensure that iOS only recognises Apple manufactured shells and it becomes a licence to print money.
And extending that even further, how about a translucent shell which uses bleed from the screen backlighting solution to power a shell that changes colour to match the wallpaper and iOS palette?
The net result would be to pull a younger, more marketable demographic to the cheaper iPhone, allowing Apple to lock them in to iTunes, Apps and then future heavy investment in Apple's product lines.
It's a lot to extrapolate from the presence of just a single feature on iOS 7, but I'd be disappointed if Apple's management hadn't at least considered travelling down that road.