I (and I'm sure many others) don't want to have to upgrade decent headphones (I have Bose & Sennheiser 'phones plus Sony buds), especially to bluetooth which need batteries/charging so are likely to run out at just the wrong time.
What I'd most like is a slightly fatter phone with a bigger...
Rumours are that the iPhone 7 won't have a headphone socket; yeah I know there will be adaptors but that means a load of gubbins hanging out of the bottom, sort of like techno hemorrhoids.