It's not a limitation of CDMA per se, but a limitation of the current implementation of the Verizon Wireless Network.
EVDO Rev A can do VoIP to the handset, where all voice/data comes to the handset as data, rather than on a voice channel. As far as I know, it will only take a network upgrade to enable this. I'm checking with some of the network engineers to see if this upgrade is going to happen and when. Simultaneous data and voice is a killer feature.