I suspect the iPhone 5 will be just as big of hit, they've been expanding to a lot more carriers, and I'm sure there's plenty of new customers (like myself) waiting to upgrade their existing phones to a brand-new spanking iPhone.
Hopefully they'll use Delta/OTA updates to keep their phone up-to-date in features compared to competitors. Can't wait to see how the Jailbreak Team's work around it as well.