T-Mobile to Sunset MetroPCS's CDMA Network by 2015

"Also weighing in GSM's favor over CDMA is the favorable roaming agreement T-Mobile picked up from AT&T when their merger fell apart."

Please this is the icing on the cake. Why would T-Mobile (run by Metro) give up the chance to have a robust National footprint? VoLTE is not dead. Metro can still transition all of T-Mobile's customers to LTE eventually. That IS the whole point of VoLTE after all. At the end of the line neither CDMA nor GSM will survive.