Disney's market share has declined substantially with the rise of Universal. In particular, Disney underestimated the money/effort/talent that Universal would put into Harry Potter, as well as the resulting public attention that Universal would receive.
In the short-term, Disney is alright because of its name, especially when it comes to families with young children. But that can change in the coming decades, as more people visit both WDW and Universal during their Orlando vacations, and return with more favorable reviews of Universal.
As a consequence, in order to maintain brand loyalty and thus longterm market share, WDW needs a multibillion-dollar expansion of the place that is inevitably (even if unjustifiably) their flagship park, the one that Orlando visitors will remember as "Disney"—The Magic Kingdom. Disney needs to think at the level of DisneySea's Fantasy Springs (in both scale and quality), to develop lands that completely blow guests away and increase park capacity / improve crowd-flow. There is land available for doing just that: to the north of Rivers of America, to the west of Adventureland, within/surrounding Tomorrowland...
Oh, and removal can be as valuable as addition: It's time to review The Magic Kingdom's lands and remove aesthetics/immersion-breaking features. Goodbye, Tomorrowland Stage. Goodbye, Aladdin's Magic Carpets. And so on.