Won't that benefit Apple and hurt AT&T? Isn't it AT&T that has exclusivity with Apple, not the other way around?

It seems like Apple benefited from exclusivity with AT&T to begin with, as a means for launching the iPhone. But now that everyone is clamoring for the iPhone, the end of the AT&T's exclusivity deal will only open the floodgates for Apple.

To me the only possible concern for Apple, as christexaport suggested, is that other carriers and AT&T themselves might not continue to subsidize the iPhone at the same rate. But I don't really see why they wouldn't, since the iPhone has been the most effective device ever and drawing in the most lucrative customers, who pay for the relatively expensive data plans and other services.