Eh, I kept an iPhone 4S for 3 years. I can live with my iPhone 6 for 1 more
For sure upgrade:
Camera needs to be the best ever on a smartphone including all Android devices. They need to at least use the same sensor that the S6 and LGG4 are using, because it is plain as day that these cameras outperform the iPhone 6. Truly they do.
4k video must be natively supported.
Battery life must improve by 2-3 hours over the iPhone 6 for general web surfing.
Some type of quick charge technology. Everyone's got it but apple. I don't care if their is proprietary or not. Just charge 10 minutes and get 4 hours of usage.
Apple omits many features compared to competition. So the ones they do include had better be the best. Otherwise what are they spending all their time doing? Then I'd accuse them of cutting features to cut costs and increase profits.
It's a short list.
I've checked out Android and all of them for one reason or the other don't quite fit me.
S6: screen brightness is low for bright retail lights (my situation). They say it's 600 nits but that's only in direct sunlight and you can't manually up the screen brightness. Max brightness indoors is something like 385-400 nits still. iPhone is 550 or so. Also do not believe that the AMOLED screens are better than IPS. iPhone 6 screen is still the best I've ever seen.
G4: Shocked that with a new battery of 3000 milliamps, the battery life is only as good as an iPhone 5s. Tested head to head under identical conditions at home. The screen is beautiful but still just insane to carry around what essentially is a tablet for piff poor battery life. The information density is also odd. Set font to small and gmail's font is way too small. Medium, and it's way too big.
M9: abysmal camera. Uneven volume. Goes to very loud at the last two levels, but that's when their pre-amp kicks in. It's kind of weird and I for one do not like their audio quality through headphones.
iPhone sound quality for music is also far better, at least it is to me. Spacious soundstage, tight deep bass, just all very engaging compared to the Androids.