20-Year Prospect
Administrative assistants are an integral part of any office—coffee can't just fetch itself, after all.
We kid, we kid. The truth is, as long as the higher-ups are too busy (or too lazy) to do seemingly minor yet essential tasks themselves, there will always be a need for administrative assistants to keep the monkeys from taking over the circus.
This isn't to say that the job of administrative assistant will be the same in twenty years as it is today. After all, this gig changes constantly as technology evolves, zapping some items off the AA's to-do list forever. Typing letters has been replaced by checking e-mail; filing expense reports, by simply submitting photos of receipts; maintaining desk calendars, by pointing and clicking on Google Calendar; and gossiping around the water cooler, by gossiping via Gchat and Skype.
In fact, tomorrow's administrative assistant is most likely to be found, not guarding the portal to a CEO's office, but in a medical facility, processing insurance claims and compiling patient data. See, the American population is aging rapidly. Since 1990, the number of people in the United States over the age of forty-five has risen by eight percent, and this slice of the population is expected to grow even bigger over the next few decades.
So, yes, administrative assistants have a future...but that future wears scrubs and crocs rather than business casual slacks and jackets.