20-Year Prospect
The Hollywood film industry pulls in billions of dollars in revenue every year, thanks in part to the work of cinematographers. Since no studio head in his right mind would want to kiss that kind of cash goodbye, we're pretty sure you don't have to worry about this one going anywhere.
Look at it this way: a cinematographer makes massive contributions to the look and feel of a film, and so affects the amount of money a movie earns at the box office. Not to mention the number of shiny gold naked guys it picks up at the Academy Awards.
And all that is before we even consider the explosion of media and content delivery in the age of the internet. It stands to reason that plenty of those new forms will require an artful eye behind the camera, so, yeah, cinematographers will be around twenty years from now.