I don't think you realize how long a century is. By the time the next century arrives, we'll all be dead. I could see it staying for the next decade or maybe two, but there's no way Corkscrew (or any other coaster for that matter) would be kept for that long. Corkscrew is not a popular coaster by any means, in comparison to Wild Thing, Renegade or Steel Venom.
Its a saying lol, don't take it literally. It just means "I seriously doubt it's leaving anytime soon". Also Corkscrew can have a very long line during busy times of the season and haunt, it might be unpopular if you compare it to bigger/new rides, or corkscrews at different parks. But in no way is it unpopular enough to get removed just do to poor demand. I mean honestly, you can say Corkscrew is a walk on most of the time, but Renegade is often a walk on too. It depends on how busy VF is, not the ride. Plus if we got rid of every ride that wasn't popular in comparison to Wild Thing, Renegade, and Steel Venom, our park would consist of only Wild Thing, Renegade, and Steel Venom lol.