In the world of cellular technology, everything comes to an end. Eventually analog networks gave way to digital. First generation gave way to second, and so on. Sometimes the transitions are easy, like retiring analog years after all phones in the wild supported digital radios. Sometimes they can be difficult and expensive, like when Cingular shut down their TDMA network, requiring many customers to make the switch from phones they liked, some being nearly new.
Verizon, the largest US carrier, followed by AT&T, Sprint and T-Mobile, has begun the latest process of network retirements, with a plan to transition all customers to LTE-only. Unfortunately for Verizon, this transition requires a lot of preparations. For example, like with Cingular, all customers will have to have devices that support LTE, which is not necessarily the case today. While it may seem like all phones support LTE today, they don't. Think about your last family gathering where you saw a flip phone. That device does not support LTE and will be completely useless after this transition.
But it's not just LTE that these devices need to support; they also need support for Voice over LTE (VoLTE). What devices currently support this technology? Well, a number of the top-end Windows Phones, Android phones and the iPhone 6 and 6 Plus from Apple. If you just upgraded your phone to an iPhone 5s, you will not be able to use that handset after this upgrade completes. There are also many other devices not compatible - it is a far easier list to find all compatible handsets.
Secondly, Verizon needs to ensure that all of its network is LTE compatible, and that they won't cut off customers who can currently use their phone if they do retire 3G. For example, at our former office in Tampa, we had no access to LTE coverage on Verizon. No matter the handset, 3G was the best we could hope for in the area. Turning off the 3G network today would leave that area without Verizon coverage of any sort.
The good news here is that this transition will not happen any time soon. Verizon has not officially announced their intentions; they have simply begun running tests in markets like Manhattan. One user discovered that their 3G access had vanished and, several hours later, was replaced by LTE running on the same spectrum. The fact that Verizon has not made this process public yet is an important indicator to the timeline. When Cingular turned off TDMA, they made their plans known well over a year before the transition began.
Additionally, Verizon's plans do not call for the launch of an LTE-only device until 2016. While that may not be entirely indicative of their timeline, it does help. An LTE-only phone would not necessarily help Verizon in this process, or even be related. Even if Verizon does not support 3G going forward, removing the radio from the handset would serve to limit the phone's roaming capabilities, both domestically and abroad. It might actually be a mistake for them to attempt an LTE-only device at all.
Once a transition like this is complete, Verizon can use the spectrum currently dedicated to supporting older technology to help them feed the need for LTE spectrum, which will ironically only increase with the transition. LTE, however, is far less spectrum-hungry than its older counterparts, which required separate spectrum for data and voice, but ran on a single radio. This means that they can get more out of the spectrum once converted to LTE.