I finally managed to get a definitive answer from Apple today. I checked twice, once over the phone, and once in an online chat to be sure. They both gave the same answer.
Anyone on the iUP WILL on pre-order day be able to reserve a phone on the iUP page of the Apple website, provided you are eligible. Obviously you will have to go to the store with your current phone to complete the upgrade when the phone is available.
Anyone on the iUP WILL on pre-order day be able to reserve a phone on the iUP page of the Apple website, provided you are eligible. Obviously you will have to go to the store with your current phone to complete the upgrade when the phone is available.