I know there was a lot of confusion about this security company Pinnacle/GE going door to door a little while back. As a resident, I got a visit from them, and promptly told them to get off my property. They spouted something about them being back after my line goes digital or some crap like that.
I contacted my service provider (ADT) and wanted to let everyone know that ADT *DOES* support digital lines from AT&T (and I believe Charter cable also), as well as Verizon FIOS (which is not in our area). These are supported nationwide, without reprogramming on the system I have. The wireless link these other guys are trying to sell are also sold & supported by ADT and Brinks/Broadview, but be advised they are cellular-in-nature and there are indeed low-signal & dead spots in our neighborhood. To be honest, I would rather trust the phone company who has been around longer than 100 years and is under regulation to provide service guarantees such as 911 service.
As a former phone company employee, I can tell you that POTS service (Plain Old Telephone Service) also known as land-line will never go away for the forseeable future, there are other services and government regulations that require this service to be provided (plus if you have no internet & phone-only like many elderly and low-income households do, the phone company will not provide digital phone service without internet service commitments). Do not feel pressured to change your system.