I agree with everyone who says that that Disney doesn't want to make any major improvements at the Magic Kingdom until attendance decreases.
From a business perceptive this makes sense, but only half way. Right now they are using the Magic Kingdom as a "cash cow". People come and attendance records continue to increase so they see no need updated or make any extensive improvements.
However, many of these people, especially first time guests, leave disappointed and less likely to return. I've had many guests tell me that the Magic Kingdom was not near as good as they expected it to be and thought that it needed improved. Many simply find it outdated. Of course everyone comes because it's the flagship park that is used in all of the ads and marketing campaigns, but its image can only last so long before the word gets spread that the park needs some major refreshment.
If the company holds out on the restoration and upgrade process of the park too long they are looking at a seriously costly issue later on. Everything will have to be upgraded simultaneously, the word will already be out that the park is in need of repair and they will have to spend extra money communicating to people that they have made the needed changes.
In the end, I think it would be much wiser to make solid improvements and upgrades over a longer period of time, than to let the park fall by the wayside and have to fix everything at once and try to restore a tarnished image.