This is not true. The Bionic has a fully GSM capable MDM6600 chipset, but the GSM bands are disabled in the radio firmware. There is no hardware incompatibility for having a completely global CDMA/LTE/GSM device, it's just VZW not having the network and billing infrastructure in place to make desirable(profitable) to do so. Motorola has already made the device capable of supporting all the bands, including the diversity antenna required.
The D4 has been reported to be slated for an update that will enable the global GSM radio bands and be the first such device available on VZW. No time frame has been released or even official confirmation of their intentions.
Digital alchemy for the Droid and beyond.