Won't happen - imagine no subsidy for your iphone
It won't happen for phones.. the deal that operators have at the moment is that they are allowed "reasonable" lockin periods and in return they offer subsidies for the phones. So if they are not allowed to have lockin periods and people can jump as they wish, then they can't offer subsidies.
I buy my iPhone from Vodafone, and get a 400€ subsidy... next day I switch to using a different operator who can offer a cheaper usage package as they didn't offer any subsidy.
So summary.. will people buy iphones when they have to visibly and upfront pay the apple premium?
PS: ipads are sold unlocked without subsidies so this works for them.
PS: might be the best thing that could happen for an operator if they got out of this stupid subsidy wars... that's what gives all the money to Apple