Your odds of remaining an EMT depend mostly on you. There are more than enough available jobs. The question is whether or not can you handle everything that comes with the work. Turnover (not the apple kind) for this occupation is about 11% annually. Do you really want to be washing blood and vomit off your clothes and equipment all the time? Do you enjoy leaving uneaten meals at the restaurant? Can you handle ER doctors always telling you what you did wrong? Volunteers are more likely to leave than paid staff.
Stress is a fact of life in this job, and over time it can wear some people down. Another factor is the relatively low pay, especially for basic EMTs, considering the life and death responsibilities they have (Ten bucks an hour?). The need to work long shifts on an irregular schedule doesn’t help. Benefits, especially for private sector services, can be limited. Some people are unwilling to go through the continuing training and re-certification requirements. Of course, not all of the turnover is bad. Advancement to other healthcare jobs accounts for some EMT openings.