I think the notion that Apple would ever buy AT&T is ludicrous, even more so than previous rumors that Apple would buy Sony, however, Apple has thought about creating its own wireless service before, and I can very well see them doing something like what's explained in the article below. Steve Jobs definitely hates that customer satisfaction with Apples products rely on another company. Apple's business model is to build the "whole widget" which includes all services related to the product. Some sort of Apple wireless carrier makes sense, I wouldn't be surprised if they tried something in the future.
http://www.todaysiphone.com/2011/02/could-apple-become-its-own-iphone-carrier/
http://www.todaysiphone.com/2011/02/could-apple-become-its-own-iphone-carrier/