What are Cellular Generations?
Cellular communication has developed greatly over the years. In one area it has developed is the amount of information that can be sent wirelessly. As technology has developed, more information is able to be transferred. Each level of technology that has delivered a different level of wireless communication has been classified into what they call "generations". The first generation was called 1G (1st generation). Each successive generation of technology has delivered more information, so 2G delivers more than 1G, and 3G delivers more than 2G, etc. The most current generation in the U.S. is 4G LTE.
When a technological generation has run its course and more advanced technologies come to replace it, the older generations are "sunsetted", which is a nice way of saying "shut down". For example 1G has already been "sunsetted", meaning that any device that runs on 1G technology doesn't work because it doesn't have the capacity to handle the amount of information that is coming across from the current generation of technology.
The same thing, that "sunsetting", has already started to happen with 2G technology.
Who is Responsible for the Changing Technology and the Accompanying Coverage Provided to Customers?
Cellular providers like AT&T, Verizon, T-Mobile, etc. drive the change of technology. Thus, anyone who uses cellular devices, from regular customers to large-scale businesses, are beholden to the technological changes implemented by cellular providers. So when a generation of technology is "sunsetted", it is the cellular providers who are putting an end to the service of that particular level of technology.
AT&T is going to sunset their 2G service. TMobile is retaining their 2G service until 2020.
What's Going to Happen to Devices on 2G?
Since the cellular companies have already started to sunset 2G technology, eventually all devices with 2G technology will stop working altogether.
AT&T's 2G technologies will cease by 31 December, 2016. That means that any and all devices still using AT&T's 2G technology by 12/31/2016 will stop working.