The LG Revolution is going to be the first phone to offer VoLTE. That mean right now phone conversations happen on 3g and data happens on 4g. No release date on the Revolution but can say it will be one of the last 4g phones to come out because of VoLTE
No phone conversations happen on 3G in CDMA systems. They all happen over 1X-RTT. 3G (EV-DO) is data only.
And I don't think Verizon is going to tiered data unless they have another trick up their sleeve to compete with AT&T.