Earlier quoted context omitted.
I bet Steve would want to for a long time. But it's an exclusive deal, so AT&T has the upper hand here, i think. If the rumours are true, AT&T has a 5-year-exclusive contract with Apple. That's still a lot time left. Ironically, this exclusiveness is some sort of lock in (from at&t's side) and here it's widely considered harmful :) Meanwhile androids infiltrate all other major networks..
If things get bad enough, can't Apple buy out the rest of the contract ahead of time?
The cost of doing that depends on the contract.
How much do you think that Apple should pay to do this? How much do you think that they're willing to pay? (My guess is that Apple isn't willing to pay more than they'd make by doing so.)