20-Year Prospect
Air travel has never been more popular, and there's no reason for that trend not to continue (source). There's no faster or safer way to travel, and over the next two decades it doesn't look like anything will beat out flying in the "Most Popular Way to Get There" category.
Demand for airplanes will increase, airports will expand, and a whole lot more luggage will need to get from Point A to Point B. This means there'll be plenty of opportunities for baggage handlers to work and grow within their field—which could possibly be an actual field, if the airport's new runway extension isn't built fast enough.
As for the job itself, you might expect technological advances to improve the way you do your work. In reality, we're not exactly sure how much more advanced putting bags into carts can get. Maybe one day you'll be hover-porting them? Who knows.