LTE is more spectral efficient, but it's expected that GSM will outlive 3G technology (WCDMA, ie. UMTS/HSPA) due to the low cost of deploying and ability to run

LTE is more spectral efficient, but it's expected that GSM will outlive 3G technology (WCDMA, ie. UMTS/HSPA) due to the low cost of deploying and ability to run on very small spectrum slices (200khz, can be done with only about 1Mhz of spectrum so long as the network is planned carefully due to channel reuse) Carriers that can get away with running GSM in their guard bands often do to support legacy M2M devices and international roaming customers.