I chat to a Vodafone upgrade specialist today and he was being brutually honest and said I may as well wait a few days and see what Apple are offering before making a decision as it may be cheaper for me. Generally they try to talk you into upgrade/buying a contract with them there and then.
Truth be told, the front line people know just as much as we do, they may only know more about the actual process of what happens after the Apple announcement.
Maybe higher up they have more information and the carriers have already devised the plans/contracts/prices of the phone(s). I don't know.