The CDMA Development Group announced provisions for SVDO, or Simultaneous 1x Voice and EV-DO Data in 2009, but there hasn't been much news on it since.

My guess is that Verizon will just continue upgrading its network for LTE instead of making this interim upgrade.

They stated at CES that they'll bring simultaneous voice and data; I'm assuming that's SVDO but perhaps they're doing it some other way.

From Q&A at CES:

"Q: What about simultaneous voice and data? A: Some devices will. Q: Just some devices, not all? A: Not ready to comment at this point."