Carriers maintain that the increasing cost of maintaining CDMA networks for a decreasing number of subscribers is not financially viable. While the cost operating CDMA networks is increasing while the revenue that supports it is evaporating it is the radio frequency spectrum that CDMA networks are using is the real valuable commodity that carriers need to repurpose for their modern HSPA and LTE networks.
To find out if your phone will lose service at the end of 2015 turn it off and open the battery compartment remove the battery. On the label with the barcodes and long numbers if one of those long numbers is labelled ESN then you have a CDMA phone that will need to be replaced.
Cellular subscribers who are keeping an old phone probably doing for a number of reasons. Those who are just using the cellphones just for making phone calls and maybe basic texting can get a feature phone for use with modern HSPA networks. Others holding onto old handsets are doing it to hold onto an older cellular plan that give more or charge less. Cellular carriers are going to unwilling to upgrade hardware leaving an older plan in place. If this case the solution is to buy an off the shelf prepaid cell phone and ask the cellular carrier to transfer service to the purchased prepaid phone.
Some especially in rural areas are often hanging onto those old cell phones get service where newer phones do not. Current CDMA uses the 850 MHz band which is best for rural areas because the signals travel farther than higher frequency bands. When CDMA gets shut down the newer network technologies will take over 850 MHz band the performance of HSPA and LTE will match today's CDMA phones get today in rural areas.
American visitors to Canada on Verizon or Sprint will need to know after December, 31, 2015 their phones that use CDMA for voice calls will no longer functional, however LTE data service will be available. Sprint and Verizon subscribers with compatible phones that have dual CDMA/GSM voice radio hardware will have to their Verizon or Sprint to get a SIM card that will enable voice roaming on Canada's HSPA networks.
The end of CDMA service may just seem like a cash grab for cellular carriers but it's just like other transitions in technology. In order to advance to what is new it means letting go of what's old.