It turns out that despite the initial launch of Verizon's iPhone 4 lacking support for simultaneous voice and data capabilities, the iPhone 4 does provide support for the 1xEV-DO Rev. B standard. This support for 1xEV-DO Rev. B could allow Verizon in the future to upgrade the amount of bandwidth delivered to the iPhone with a simple software upgrade to their cellular towers. 

The additional impact of 1xEV-DO Rev. B is the reduced latency by using statistical multiplexing across channels will enhance the end user experience for latency sensitive services such as VOIP. Many people have been discussing the fact that Verizon currently does not support SV-DO, however Qualcomm's support for simultaneous active 1x Voice and EV-DO data support has been in the works since 2009.

The support for 1xEV-DO Rev. B in the MDM6600 chipset can be found in documentation on Qualcomm's website here.