For those saying the only thing holding WDW back from reopening are state decisions...the unfortunate thing is that different types of businesses are going to reopen at different times. And the nature of WDW means it will likely be one of the last types of businesses to fully reopen.
For reference, I live in NYC and work in the theatre industry. The Broadway League has already said that September is best case scenario for Broadway reopening. Why? Certain social distancing measures would be impossible to enact in a theater while still make a dime. For instance, Cutting the capacity of houses is not financially feasible, the margins are too slim. The industry also depends on national and international tourism, and there are still too many travel restrictions in place. Not to mention fear and financial hardships. My organization has already made the decision that we cannot reopen until December. Other businesses in NYC will open before us. Office buildings, some stores and restaurants, places that can more easily implement social distancing and other precautions. Places with massive gatherings of people are going to be the last on the list, and the places that are most direly affected: theater, clubs, sporting events, concerts, theme parks.
I realize that WDW is not NYC. However, Disney does rely on massive amounts of national and international tourists to make their profit. Many people will be unable to travel for a while, due to restrictions and/or financial loss. And every type of social distancing or sanitizing measures in the parks just raises more questions. If you socially distance queues, lines will back up into the walkways causing congestion there. If sanitizing after each passenger slows down the ride, where do people go to wait in these VERY long waits? If they discontinue meet and greets, will enough people buy memory maker? If you remove seats from restaurants, will they be able to turn a profit? Will people even be willing to take their "once in a lifetime" vacation in a pandemic if half of the activities are removed or altered? Its like Hercules cutting off the head of the hydra only for three more to appear.
2021 does seem like perhaps a worst case scenario, but it is certainly possible. I'm more leaning towards September in my reopening predictions (maybe Springs and/or some resorts are opened prior to test things out). Unless we have all of Disney's budgetary numbers and contingency plans in our hands, none of us know the answers. But you can bet a 2021 opening is one of the many options on the list.