We're rapidly moving to an all IP world. Today we have in some markets Mobile Wimax from Clearwire. Their using the Sprint IP network and WiMax. In the future LTE is coming to Verizon and eventually AT&T. We're also seeing devices that will make computers mobile phones with data built in.
Current 3G technology permits voice to run over it, but it's not always perfect. LTE and WiMax are ready for voice. It's all just a matter of time and is no longer a if, but a when.