20-Year Prospect
Realistically, in twenty years this job could be taken over by androids—or, more likely, the software that turns voice into text could get far more sophisticated. It might even learn how to correct grammar and understand people who chomp down on Subway sandwiches while giving dictation. Smartphones and mobile computing are already rapidly changing the landscape of speech recognition (source).
It's not a sure thing, but it is possible that speech recognition could cause medical transcription to become extinct. Right now the technology isn't good enough to not need people in this job, but the job has definitely shifted over the years with the advent of dictation software.
This might be a nice side-job to pick up while working towards furthering your education, as the hours are flexible, but it's probably best not to plan on jumping in for the long-haul.