I doubt VoLTE will make any practical difference in day-to-day usage, unless carriers allow customers to default to a custom SIP/IMS registrar -- which won't ha

I doubt VoLTE will make any practical difference in day-to-day usage, unless carriers allow customers to default to a custom SIP/IMS registrar -- which won't happen for a long time. Calls (signaling) are still routed through the carrier[1], and your carrier still has to interconnect with the other end. While most backbones have been all-IP for a long time, the copper/cellular last mile is still mostly circuit-switched, even more so internationally. [1] I'd be very surprised if VoLTE traffic, including media, was sent over the public Internet at the same QoS as the rest of your data. Voice-over-LTE is a nice technical achievement -- IIRC reliability was very difficult to ensure, especially during 3G/2G handoff -- but to consumers, VoLTE means nothing.