Oh, I agree, but as time goes on, things inevitably change. And it's not necessarily that they aren't sure of what's going to happen, but there can always be last-minute shuffling of plans. New Fantasyland is a perfect example. The plans were shown (at D23, I think?) that didn't have Seven Dwarfs Mine Train, but rather a pixie type area with a spinner ride (like the Mater ride at DCA). But then, very late in the process, Seven Dwarfs Mine Train was added to the project, replacing the pixie area. I'm not sure if construction had already started when they made that announcement, but it just goes to show that plans can and do change at various stages of the game.