If you’ve been expecting a massive rush to leave AT&T for Verizon, then think again — customers on Apple’s formerly exclusive iPhone network may not be completely satisfied, but they are pretty much locked-in — at least, 90 percent of them are.

Susquehanna analyst Jeffrey Fidacaro told Digital Daily he thinks the carrier stands to lose two million iPhone users “at most” to Verizon. This is because when AT&T offered an early upgrade scheme for existing customers pining for an iPhone 4, it also managed to lock them into a new contract with a $325 termination fee.

Verizon will sell plenty of iPhones — but it may not grab too many AT&T switchers. As Digital Daily observes, former exclusive UK iPhone carrier O2 has said it has no evidence of its existing users switching to new UK suppliers “whatsoever”.

The notion of a 10 percent switch rate is under the percentage predicted by a Changewave survey taken earlier this month. This claimed 16 percent of AT&T’s iPhone customers were planning to leave the carrier (see chart ).

May last year saw some analysts predict 40 percent of AT&T’s iPhone customers could run to Verizon. This proves the difference an early upgrade deal to iPhone 4 might have made — and also hints that the move to a multi-carrier strategy was executed in such a way as to help Apple’s old partner minimize impact on its business.