AT&T’s press release announcing the iPhone 5 notes that current subscribers can continue to use their existing data plans with the new iPhone 5. They won’t be forced to choose AT&T’s newly announced shared data plans.
Subscribers who are grandfathered-in to the now-extinct unlimited data plan can continue to enjoy unlimited data on their iPhones, even if they upgrade using AT&T’s subsidised pricing.
The relevant bit from AT&T’s press release:
We offer customers the flexibility to keep the iPhone data plans they already have or choose any of our individual or new Mobile Share plans. We’re proud that more customers choose AT&T for iPhone than any other U.S. carrier and look forward to making iPhone 5 the newest addition to our lineup.
You’d of course be throttled if your usage goes past a certain limit, but that threshold has been increased to 5GB from the earlier 3GB.
This is great news for existing subscribers, who get to upgrade their unlimited 3G data plans to 4G LTE, with the only downside being that you won’t be able to use FaceTime over Cellular due to restrictions imposed by AT&T. The carrier allows FaceTime over Cellular only on its new shared data plans, which are more expensive than the older data plans.