Instead of releasing separate iPad 2 models for AT&T/GSM and Verizon/CDMA, why doesn't Apple just use that new Qualcomm dual-mode chipset and support both GSM and CDMA on one device? That way users could not only swap microSIMs and move between different GSM/HSPA networks when they travel abroad, they could switch between AT&T and Verizon's CDMA/EVDO networks when at home. (For an explanation of what all those terms mean see TiPb's data and wireless networking glossary.)
Well, if the Verizon iPhone is any indication, Apple may indeed be using Qualcomm's MDM6600 dual-mode chipset, only enabling CDMA on the Verizon version. However, the radio is only part of the equation. The other part is the antenna. Supporting different frequency bands requires different antennas at different lengths.
The AT&T/GSM model supports 850, 900, 1900, and 2100 MHz for UMTS/HSPA, and 850, 900, 1800, and 1900 MHz for GSM/EDGE. That's 5 bands (pentaband) already.
The CDMA/Verizon mode supports 800 and 1900 MHz for CDMA/EVDO rev. A. That's 2 bands (dualband).
If -- and I'm no radio engineer so I don't know -- the same antenna could work for both GSM and CDMA on 1900, Apple would still have to add the 800 MHz band for a minimum of 6 bands (hexaband) to support both GSM and CDMA in one model. (It might also require more or different internal connections on a tiny, tiny motherboard.)
While it's never wise to underestimate Apple, they may simply not be able to engineer a hexaband antenna at this point. (No death-touch jokes please.)