To answer the question, I don't think WDW is going to close because of rising cases in Florida, but here are some circumstances where I could see them closing.
1. If the state ordered them to close, they would close. I can't see this happening as Governor DeSantis wants tourist dollars.
2. If at some point in the future they studied their profit-loss statements and decided that reopening was doing more harm than good to them economically. This might happen if it seems like the virus is going to continue for many more months and the situation in Florida or the country as a whole is such that not enough tourists will go to the parks and resorts to make opening them financially viable. They'll take some short-term loss in the hopes of ramping up numbers and turning a profit, but that can't go on indefinitely.
3. If the damage to their reputation is so great that they consider the potential long-term damage to not be worth any short-term profits they're making. I think this would only happen if there were many cases that were traced back to Disney and it got spun up in the media really bad for an extended period of time. They're helped a little in the fact that Florida contact tracing is really awful, so it'd be hard to pin anything on them. But other states are doing a better job of contact tracing. There is an instance right now where New York has traced an outbreak in one of their counties from people who traveled to Georgia and brought it back.