To be honest, current management seems to think that homogenizing the Disney experience across all for parks is the way to go. Essentially, we would end up with four versions of the Magic Kingdom, which whilst wouldn't be a problem I think it would potentially make the whole experience less repeatable and more samey. Personally, I think they need to do the opposite. Look for ways to clearly differentiate the four offerings from one another:
Magic Kingdom stays as is with updates to less popular attractions but kept true to its core theme.
Epcot needs to move more heavily towards science, geography, history type topics with pavilions that link to these themes such as medical advancement, emerging technologies, food production, it could look at robotics, architecture, transport. The key would be in making the experiences both engaging and repeatable. That is why Test Track and Soarin' work well. I also think the park could have more focus on history, in the way that Spaceship Earth celebrates how we have got to where we are now. This would solve the problem of things going out of date. I could certainly think that a Pavilion sponsored by Apple for example could work, where they could showcase and sell new products but have the pavilion as an experience within itself, almost an Apple Store on Speed. Providing the experiences are fun they will be repeatable.
Studios I'm not really sure what to do with, but I would think they could successfully move it towards thrill rides and this would be successful. Aim for the teens/young adults too cool for Disney otherwise crowd. Go after the groups that would otherwise head to Universal/Busch Gardens etc. If the rides are good enough people will want to go. This could be mixed with slightly longer Broadway style shows which if kept fairly fresh could work. The issue with the shows is they are left in place for far too long. I would also move the hours so that the park is open later in the evening, possibly opening slightly later in the morning in order to accommodate this. Have a good mixture of shows (which could all be pre-bookable so that guests could hop across in the evenings after a meal and watch a performance. If the seating areas were large enough these could be fairly lavish with fully costed sets and to a higher standard than typical theme park shows. Up-sell preferred seating for those with the big $. I also think the park suffers from its visual theme, there are too many plain buildings - the studios theme is long gone so they need to bury it now and make the park as immersive as the other three.
Animal Kingdom feels cohesive as it is, Pandora feels like a good fit in my opinion. The current theme and range of offerings feels strong. Just more of the same would work.