Now as it seems likely the iPhone is finally coming for Verizon Wireless customers, it means that Apple will be offering an iPhone 4 as two separate products. To look at they will seem identical but on the inside they will be completely different.
Both handsets will be completely incompatible with each other, and each device will only work on their dedicated networks. You will find it hard to tell the difference from the outside, and only when turned on will you be able to distinguish between the two with the operator logo.
Once any iPhone 5 is released this should coincide with AT&T and Verizon having a 4G network. The need for users of each carrier to remain backwards compatible with each carrier’s incompatible current-generation networks means that the iPhone 5 may have to be available in both versions.
Buying the device in U.S. means you are tied in to a two year contract for the first part of the phones life, so there might not be many people changing networks during the current devices lifespan anyway. This means that the iPhone 4 and any iPhone 5 will be available as two physically different, physically incompatible, yet physically identical handsets.