What features would an iPhone need so that you never felt like wanted to upgrade ever again?
The ability to upgrade discrete parts without purchasing a brand new phone. Settle on a screen size option, purchase a processor, memory and ram, company assembles for you custom. In a few years, parts are old, you send back or take in, pay a little bit and replace that part.
Solves theft issues, makes every product personal..
Not exactly the answer to your question but that is the only way I could see keeping roughly the same device for long periods of time.
That didn't work all that well for desktop pc's and I don't see it working here. You can spend a lot of money on individual components only to be left with a bottleneck somewhere else. Otherwise, I would have kept my Pentium 3.
What features would an iPhone need so that you never felt like wanted to upgrade ever again?