I believe VoLTE and WiFi Calling has been implemented by multiple carriers. (Telus, Ro****, Fi**, Be**, Vi****, etc.)
I also recently saw that Koodo is currently testing VoLTE and WiFi Calling.
https://mobilesyrup.com/2017/09/19/koodo-says-volte-wifi-calling/
PM probably won't have VoLTE and WiFi Calling in the near future since it is a prepaid service but it would benefit a lot of users if PM eventually implement them.
I don't think it's an unreasonable request since Telus/Koodo/PM all share the same network infrastructure so it's just a matter of testing and implementing it at PM even though it may not be the first thing on the list.
Let me know if you think otherwise. Thanks!