For the last several months Walt Disney World has been operating at about 35% of total capacity. The need for social distancing has limited the number of people which are allowed in the park at any given time, which has in turn limited what the theme parks are able to offer. Not all Disney World cast members have come back to work since the parks reopened because there simply aren't enough people in the parks to justify opening every attraction, gift shop and dining location. However, the state of Florida just made a major change to its pandemic rules, which has potentially opened the door to let Walt Disney World let more people in the parks.
Based on the number of vaccinated residents of Orange County, Florida, Walt Disney World's home county has entered what is called Phase 1, which, among other things, reduces physical distancing requirements from six feet to three feet. Nexstar reporter Scott Gustin confirms that theme parks have been made aware of the change, which will allow all Florida parks to allow more people inside the gates as they are now allowed to be closer together.
The fact that Walt Disney World and Universal Orlando Resort now can allow more people inside the gates doesn't mean that they necessarily will-- though it seems likely. Cutting the social distancing requirements in half would seem to mean that potentially as much as twice as many people can fill the same space. I wouldn't expect to see the parks jump from about one-third capacity to two-thirds overnight, though we could see a slow increase over the next few weeks and months.
Disney has generally taken a slower and more methodical approach, adjusting the rules inside the parks as new data reveals best practices. We haven't seen Disney Parks simply make changes based on what will make them the most money. While Disneyland is technically allowed to allow vaccinated individuals from out of state to visit the parks, thus far the park has limited its reopening this week to California residents only. This despite the fact that Disneyland and Disney California Adventure still have plenty of reservations available for the next few months.
As with so many things, there will be a financial calculation to make. Increasing the number of guests will require Walt Disney World to open up more of the resort. They'll need more hotel rooms, more restaurants, more shopping, etc. And that will likely bringing back more furloughed workers. Disney has always said that making Walt Disney World a net positive financially was important, and thus the parks will want to find the best balance where the money coming in exceeds the money going out, which could mean the park could run at a lower than allowed capacity if it makes financial sense.
While Walt Disney World still isn't hitting full capacity at its current levels most days, it does hit them sometimes, so the demand is clearly there to add more space inside the parks, and as more people become vaccinated there will likely be many more willing to make the trip to Walt Disney World.