Odds of Hanging On
Sure, some medical assistant positions could be filled by Clyde the orangutan. However, if you're willing to challenge yourself and pick up as many specialized skills and certifications as possible, then you'll have no problem keeping your job and finding a new one whenever you're ready to move on to something different. Doctors are always going to need experienced clinical medical assistants on hand to help them handle those mundane tasks that don't require a medical degree.
Keep in mind, though, that the work done by administrative medical assistants is expected to change over time as medical facilities make the switch to electronic health records (EHR). If you want to move up from your position as phone-answerer and appointment-maker, you should familiarize yourself with EHR computer software and keep up-to-date on how electronic data can be used to improve healthcare delivery where you work.