FaceTime over cellular networks seems to only be coming to the new iPad and the iPhone 4S.
This may seem like a desperate attempt by Apple to keep people upgrading to newer devices every year, but FaceTime over cellular networks will join Siri and Maps’ new turn-by-turn directions as an iPhone 4S and New iPad-only feature regardless of older devices such as the iPhone 4 being capable of the features.
The iPad 2 and the iPhone 4 are FaceTime-capable devices that would not be getting the ‘over cellular’ feature in iOS 6, despite having A5 processor. The 4th Generation iPod Touch never had cellular service from the beginning and it will not be getting it now either.
Although the news is a disappointment for people owning older iOS devices, anyone with the newer iOS devices like the new iPad and the iPhone 4S must be happy to knowing that the feature will be there in their device. Older devices will have to wait for a jailbreak-based solution to get FaceTime over cellular networks.
If you cannot wait for a jailbreak, then as an alternative, an older device could tether (or share a cellular connection) with any other tethering-enabled iOS device to use FaceTime from anywhere without a jailbreak.
Most older iOS device users will be able to make do with third-party FaceTime alternatives such as Skype and Tango because they are widely used by iOS users. Additionally, users can still use Wi-Fi as usual.