Why should iUP customers get any preference? Lots of people upgrade and buy new iPhones every year along with Apple Care, without being on the program. Doesn't mean they're less loyal than the ones on the program. I got a 7 last year and will be upgrading to an X/Edition, which is a bigger jump than many people will be taking, most will simply be upgrading from 7 to 7S or 7+ to 7S+, shouldn't I get a preference for going from 7 to an X/Edition which will cost me a lot of money?
The program is simply for your convenience, so you can easily upgrade every year without going through the process of trading in the phone at a carrier/third party store, paying off your contract and taking a new contract. It's not some sort of exclusive or loyalty program where people are supposed to get some sort of preference over others who are equally as loyal but not in the program, and I really hope Apple doesn't do this sort of thing.