But the thing is, I would think that the main reason people do ride any of the "older" attractions in the first place is because "we payed the admission for the day, we might as well see everything", and they don't have much else big to see after things like Mission: Space and Test Track. A lot of people do not know what to expect when they go on attractions like Energy, Living Seas, or anything in World Showcase. For all they know, these "first time" visitors, or visitors who haven't been there in a while and don't remember much, could expect anything from a stage show, to a kiddie carnival, to a big, superspeed rollercoaster when they go in to pavillions like these. Unfortunately, I am sure many are dissapointed after going on some of these older attractions, not realizing they were going to be lectured on things like growing fruit or how dinosaurs provided us with fossil fuels. I hear it just about everytime I go on these attractions.
So if a new ride did take away guests from these other, older attractions, wouldn't it benefit Disney, as the new ride could be a successful replacement to the rather tired attractions that have been there for many years? Yes, they might then end up completely shutting down the attraction/attractions that the new ride has taken its visitors from, but at least you could be sure that guests are coming out of the new attraction happy and satisfied, as opposed to bitter and bored.
And I'm not saying that the big, new attraction has to be a rollercoaster or anything. I firmly believe that, with the technologies Imagineering toys with these days, they could make a fun, state of the art, educational, family-friendly ride that could also be very popular and successful at Epcot.