IMO, outside of the tech world, nobody really cares about USB-C - or at least - not enough to drive upgrades. It's just what one end of the power cord looks like.
For people who already have USB-C phones and are considering switching it means "All of the cords you have right now will still be useful", which is a definite improvement over "All of the cords you have right now are junk you will throw away and have to replace with new cords".
I'm not trying to say that will drive massive upgrades in and of itself, but I can definitely see it being a nice-to-have at the margins and help a nontrivial set of people pull the trigger.
I'd think most potential upgrades to the next iPhone would be current iPhone users. If anything, I think the switch to USB-C would be a deterrent to people who are sensitive to cord changes.
I don't understand the need to have a single connector vs a block with interchangeable cords, but I also don't care that much about it so I might be missing something.
Don't you have USB-C cables for literally everything else? This is Apple's equivalent to finally dropping micro-USB, everyone is using USB-C now, thankfully.
I mean my MBP has a MagSafe charging port, but I use USB-C for powering that too. One type of cable for everything.
You know what we had to do about a decade ago? Toss out our 30-pin connector cables. Times change, the switch of the iPhone to USB-C was inevitable given that Apple has already moved pretty much everything else away from the Lightning connector already. At best the EU pushed up the timeline.
We're about a decade out from them changing from 30 pin to lightning and I still occasionally hear someone complaining about apple "always changing the charging cable" so I imagine it's actually going to piss off the general public.
For some people its a deterrent. I talked my coworker into an AppleTV earlier this week and the new remote was USB-C charging (doesn't come with a cable) and he was upset that he couldn't just charge it with any of his existing lightning cables. I tried to explain to him that in no time at all his house would be inundated with usb-c cables everywhere, but he was not happy.