Sprint will face a bit of a challenge, however, because it will sell only the iPhone 4S and it will have to charge "somewhat premium rates" for that device, said Burden. Meanwhile, AT&T will carry the iPhone 4S but it will also be able to offer the iPhone 3GS for free and the iPhone 4 for $99 (with two-year contracts in both cases). For its part, Verizon will be able to sell the iPhone 4 for $99, in addition carrying the new iPhone 4S.

In comparison, the iPhone 4S will sell for $199 for the 16GB model, $299 for the 32GB version, and $399 for new 64GB version.

The new iPhone 4S also functions as a world phone that works with both CDMA and GSM networks.

That means that customers of Sprint and Verizon, which have CDMA networks, will have to use GSM networks if they travel abroad, since GSM is widely deployed globally. And they will also be subject to roaming policies and will have to pay rates that can be quite high, analysts noted.